NZ to US Travellers

A couple of mates & I are wanting to road trip from NY around the country & end up in NY again, probably go from New York to Seattle, then down to San Diego stopping at all the normal sightseeing places, across to Florida, with more sightseeing, then back up the East Coast. We want to stop in as many places as possible, we probably prefer the night life and amusement parks over scenery but we are very keen to see as much as possible. What kind of time frame would be acceptable for this kind of trip, we probably have 6-8 weeks or maybe more depending on the money sitation. As I have been looking thru this site for a couple of months now I sort have got some ideas but this is our first road trip & we don't know much about USA so any info would be great. Thanks.