Welcome gunbuster!
Let me be the first to welcome you to the big A! Yes, it's a great site chock full of usefull info. Welcome to the addiction!
As to where you can detail your Beemer....hmmmm, good question. You're certainly at a disadvantage not having your own working space. I'm one of the fortunates that has his own home, garage and long driveway! However, I'm thinking that a local park where you can find a corner away from any activity should allow you to detail all day, and since you're not using a PC you don't need to worry about an electrical outlet.
Hopefully someone else can come up with a good suggestion.
Good luck !