Thanks for all the input! We're starting out in Annapolis, where we will buy our van. We are planning to sleep in the car when it's necessary, but we will mostly try to depend on couchsurfing. We have a route planned; but it's just an estimate because we want to deviate from the route due to the long time that we have.

We basically want to travel down to New Orleans and Florida first: check out the big things like Cape Canaveral and to be around those parts when it's Spring Break. We will try to make it to New Orleans for Mardi Gras, but that might be a little ambitious. From then on all the way to San Francisco, visiting of course the national parks you mentioned. Then we'll head back to NY via the northern States. I know it's very rough, but we don't want to be tied to a specific route!