Both the 250 and 500 will be sufficient for riding around town. A 500 will be more comfortable than a 250 if you find yourself getting on the highway. Based on your post, it sounds as though you'd be pretty happy on a GS500. I rode one around for a while and found it to be a lot of fun without being intimidating. You'll probably want to go sit on various bikes to get a better feeling for what you want.

The cruisers tend to have lower seats, which can do a lot to improve confidence for shorter riders. The SV650 is a relatively sporty bike while still retaining good comfort. SV650's are relatively desireable which causes them to hold their resale value pretty well, and even if you crash one, if the frame is straight, you should be able to sell it as a racebike pretty easily.

The GS500 has more of an upright riding position, with a relatively low seat. They're mostly unchanged from the early 90's until 2004 I think where they got some new plastics to make them look sportier. A used one should be reasonably easy to find for a good price.