By streetbike do you mean a sportbike or cruiser?
Either way, don't let anyone (especially the dealer) talk you into a bigger, faster, cooler bike. You can always upgrade and a bike that's too much will scare you more than you'll enjoy it anyway. I saw a guy leave a brand new $10,000 bike in the garage for almost two years before he finally sold it. It was just too much for him, but was talked into it by friends.
Good cruisers, in my ever so humble opinion, to start on would be a VStar 650, Honda Shadow 750, or maybe a Sporster if you want to spend a little extra cash and wouldn't cry when you dropped a Harley. You can get insured on one of those first two for about $200/year. I'm not a huge fan of sport bikes, but anything around the 600 mark would probably be ok. I hear the YZF600 (not the R6 or R1) is a pretty good first sport bike. Of course there's always dirt. Cheaper, more fun, and it doesn't hurt as bad when you go ass over end.
I know you said you were going to take the safety course, but start there. Don't buy a bike and then go. It'll give you a better appreciation for what you can (or want to) handle.
Just my 2 pesos.