1) I started at UP. At first, I wasn't a fan of the very large classes and the fact that most classes were taught by TAs (for some classes, I barely saw the professor). As I progressed into engineering classes as well as higher level classes in general, I enjoyed it greatly. It became more intimate and you received significantly more face time with professors. The learning environment improved greatly. With respect to the social aspect of college--no complaints. A ton of stuff to do, lots of people (mostly friendly, not a clique-ish environment, in my opinion). It's what you'd expect thought--a small town in the middle of nowhere with a lot of college-aged kids crammed into it. And they all have a "PSU vs the world" mentality, which bodes well for all PSU students, but not so much outsiders. Some of the 2+2 kids were a little clique-ish though. You'd notice them hanging around their group of friends that transferred with them and not always interacting with the crowd--this usually goes away in time though.
In brief--if you like a city atmosphere, and all the social upside (and some of the downside) that comes with it--you'll like UP.
2) I was pushed toward engineering/computer science/physics/chem early on because I was a huge math nerd.
Why not comp sci? I had already had 4 years of comp sci classes as well as a lot of self-learning and felt that 1. I can learn this all on my own and don't need to major in it and 2. It's not something I'm really passionate about.
Why engineering? 1. Math 2. Physics. 3. I like robotics. I like automation. I like building things. I like tearing things apart. I like knowing how things work and trying to make them better. I was the kid growing up who built his own PC, worked on my dirt bike and car.
I didn't declare until midway through my sophomore year. As I began taking more and more engineering classes, Mechanical seemed to fit with the things I'm passionate about. I also liked the fact that it is a highly employable major and can do a lot of different things that other disciplines cannot. I wish I could give you more of a guided approach to choosing your major, but for me it was more of a feeling really. Just finding that something that fit my natural talents and passions.
3) I can't speak for every engineering discipline--but for mechanical the job market is good. I didn't have any issues finding a job (I graduated in 2008, which if you recall was the worst financial crisis many of us have ever seen--unless you lived during the depression). I regularly get headhunters coming after me to recruit me to different firms. This isn't me bragging--it just is what it is. I'm sure the majority of skilled professionals experience the exact same thing--I'm not a special snowflake. If you are skilled in a math-based discipline, I'd reckon you'll have no issue finding a job. The only engineering friends of mine who had a little more trouble getting jobs were 2 individuals who majored in petroleum and nuclear engineering, respectively. From what they told me at the time, those fields just had a bit less opportunity. This is not the case anymore, especially for petroleum engineering.
4) PSU, overall, was a positive for my job prospects. Don't get me wrong--it's not MIT, Cornell or Standford. But, PSU actually has a very good engineering program overall (some majors better than others). Where PSU shines more than probably 99% (I made this stat up) of colleges in the US is the alumni network. PSU graduates are everywhere and they're generally always willing to help out a moderately talented individual. This is especially true if you stay on the east coast. There's an incredibly good chance that you'll run into someone in the job recruitment process who went to PSU. This will give you a great starting point for conversation with them and can be a tie-breaker down the line. People may not want to hear it, but like it or not, part of the recruitment process is hiring someone you get along with and can work well with--the smartest guy doesn't always win.
If I have 2 really impressive, and seemingly equal candidates, I need to start breaking ties somehow. If someone has PSU on their resume, I know the type of education they received, and I also have a lot of people back at the college of engineering, who I trust, that I can reach out to for feedback on that individual if necessary.
In brief, PSU will definitely help you on the front-end of the job application process. You'll get your foot in the door more. It can help you on the back-end as well, but this isn't the norm as candidates usually separate themselves through the interview process quite nicely.
5) When I went to PSU, you had to declare by the end of your 3rd semester (you should check what this is at PSU now--the student advisors there can help you out with the timing of all of this to ensure you're on the right track and do not miss an opportunity to declare or go to UP). The start of all of the engineering programs is very similar. If you know you want to be an engineer of some type, you can afford to wait it out a little bit and feel things out. The classes you're taking will count for practically any engineering major and you won't get far behind in any specific one (this is by design, of course--a lot of students do not know what engineering major to choose immediately). The sooner you know, the faster you can graduate (if that's a concern).
If you really have no idea what you want to major in at all, then it becomes really tricky. You need to try to take classes that count toward as many majors as possible (so you don't get behind), all while trying to get exposure to different majors to learn more. This is tough. Every major at PSU is going to have different entry requirements and you can put yourself in a position where it's difficult to meet the requirements of certain majors if you spend too much time figuring things out. You'll want to check for what the various requirements for the engineering majors are at PSU (I have no idea what they are now), but when I was there they all were pretty much "Math 140, 141, easy chem, easy physics, generic engi classes, C or better in all, and 3.XX GPA and above."
I hope this helps. Sorry for the wall of text everyone