One of the few issues I agree with the left on (and not all of the left) is prostitution decriminalization. Even then I might be doing it for different reasons.
Personally I'm not for "legalization" (i.e. let's regulate the crap of out it), because if the smoking trend is anything to go by, you can expect prices to go up by 500% or some ridiculous number like that due to taxes upon taxes. This is something people don't realize, the left isn't doing it for "freedom", it's not doing it on principle (same with the drugs) it's to find another excuse for control under the guise of freedom. They did it with cigarettes (no, I don't smoke and in fact I hate them, I just don't think the massive taxation is legitimate) and they're going to do it with every other vice.
Another strange thing is that many leftists are pro-prostitution but anti-pimp which is a bit like saying that you can sell alcohol, but not run a bar and hire people to sell alcohol. Given their hatred of capitalism, I'd caution against their particular way of doing things. Any push for genuine reform will have to come from the libertarian right, not the progressive left.