2004 -- Massive RoadTrip

im a 25 year old male from australia heading off on a massive road trip with a female friend from canada.we wont be leaving till next summer but want to start the planning.we will be using my friends new honda so we have the car sorted.we will be on the road for two and a half months and want to see canada as well. our trip will begin in vancouver.driving down through seattle,san fran and LA.from there we will head arcoss to new york via vagas. from there we will head up into canada and drive back to vancouver taking our time to explore, but going by the trans canada hwy. what i would like to know is what would be the best path down the west coast and the best path across the west to the east coast?
we would like to spend 3 nights or so in the big cities like san fran and LA.and are very versitile with our route but would like to stick to the interstates. planning on staying mainly in motels and would really like to make it a party trip. any tips about the route or in general would be great. thank you all very much. tom.

If you want to stay on Interstates, then you probably wouldn't want to do my suggestions, but here goes: From Seattle, head out to the coast and go to California via the coastal highway. Breath-taking scenery and, if you get bored of it or behind schedule, you can head inland from most anywhere to hook-up with I-5 South. I would head to the East via I-40 with as many forays onto Historic Route 66 as time allows. Las Vegas is just a short jaunt off of I-40. Take I-15 at Barstow, CA, and then return to I-40 via either Hwy 93 or 95. The party scene is the least important part of a roadtrip for me so I can't give you any advice in that area. Have fun!