I flew down to Orlando on an ERJ-145 recently. Like other posters have said, exit row would be good, but in general, get on the side with 1 seat as opposed to 2. It's a 2+1 configuration and I was on the left side in a single seat. The people across the row looked pretty cramped together. One positive thing, my laptop had a bigger tray table to sit on on the ERJ than on a 757 on the way back. But for leg room, I wouldn't count on it.
Dave