Well, if you are over the whole "annoyingly loud college kids stumbling down the street and yelling gibberish at 3am" thing, I would recommend staying away from Alston...otherwise, you can get decent bang for your buck there.
Also, why do you want the Red or Green-line? If you don't mind buses (which are at times more convenient anyways), or switching from the Orange-line, I have a lot of friends who love JP. You can get a lot of space for not much money, and if you are in the right neighborhood, it is relatively safe.
What area are you working in, that you would need public transportation to?
I also suggest using Craigslist, rather than going through a realtor. A lot of times you can avoid the fees that way, and save a bunch of money.
I work in Copley and live in Watertown so I currently take a direct bus to work. Most of the areas I would like to live (Harvard Square, Davis Square, Brookline, Brighton). I haven't really looked into JP, but that would be huge because the Back Bay station is near me so the orange line is perfect.
I don't really care about loud college kids, just about the quality of the apartment. I notice that a lot of the places in college student areas are dumpy which is why I wanted to avoid those areas.
Anyone with knowledge of JP want to tell sell me on it? So far Harvard is my favorite area but in order to live there I need to find a place that is a bargain for the area.
Yeah, if you are going to Copley, JP should definitely be an option. It is much cheaper than Harvard square, and you can take the Orange line, or the bus (I forget which one, but I think there is one that goes right to the Pru) right in to work. I definitely think it is an easier commute than from Alston/Brighton.
I also would say that you can find much nicer apartments in JP than in Alston anyways (In Brighton, there are some nicer places).
The main question is about the type of area. I would say that JP has a lot more hipster types, and a lot of the bars/restaurants are kind of geared towards that crowd, while in Cambridge in general, you would get much more of the yuppie crowd.
The other place you could look if you want a really short commute is the Brookline Village/Mission Hill area. There are parts of the area that I wouldn't recommend, but if you pick the right spot, and check it out first, you can sometimes find some great apartments, and it is a very short trip up to Copley, with plenty of bars/restaurants along the way (not to mention, a short walk to Fenway).
I often help my employees find apartments around here, and while its very hit or miss, there have been some really impressive places.