Teltic, I used to live in San Diego. Depending on what area of town you live in and where you work (if you want to live close to work), the 2500 will be a pretty good amount. It sounds like you need to be the primary renter for an apartment to show cost.
In order to give you an idea of costs, my condo that I rent out is a 2 bedroom 2.5 bath that rents for 2k in an area that isn't close to down town or any extremely popular area (it was around 15-20 minutes to downtown and 30 minutes to either point loma or mission valley). My average utilities for electric and natural gas were around 100 a month more or less depending on the time of the year. Internet was around 55 a month for a higher speed (around 120 if you get cable with it). Water was pretty cheap 30 or less for a 2-3 month period, it wasn't billed every month. I was, I think, pretty mustachian with my power and water usage, so a roommate would definitely add to the cost there.
If you are someone who doesn't mind or even likes having a roommate, I think that would be a great option. There are always people looking for a place to rent, it took less than 2 weeks from when I moved out of my condo until I had a renter. I wouldn't necessarily recommend living in a van, it can get pretty hot in the summer around July through September, although I have seen some people living in RVs or even sail boats. Apartments in good locations are going to run well over 2k for a single bedroom if you're talking down town, so airbnb would be a tough one. I did look at airbnb prices for where my condo was located and they were only around 35 a night, but again it wasn't in a good tourist area.
No matter how you slice it, you're going to do well! You'll have your paycheck and not have many expenses except gasoline and food! Don't do something that will make you miserable just to save a few bucks when you're already coming out ahead.