I used the yellow bank in Nathon last time I needed a chunk of USD. I think I had to wait a day, but the rate was decent. I would say any bank with the best rate on the screen, can get you USD within a day or 2.
The beach is well within walking distance, but no local bars ect. You would need a bike/truck for major shopping and excitement. Taling Gnam is a quite area in the South west near Raja Ferry.
I know a couple of friendly landlords in the Taling Gnam Area with property around the 10k mark.
Let me know if you fancy that area, and I can give you some phone numbers via PM.