I did a trip from Wisconsin to the west coast, down the coast and back to Wisconsin, as one long lesson to get an FAA IR. It was in February and the mid west was VERY cold: minus 15C on the ground.
As such quite a bit of my trip isn't really that relevant to what you're doing, but I would recommend (mostly echos of what has been said): Sedona, Catalina Island, Crater Lake in Oregon, flying over San Francisco bay, statying at the hotel in Santa Maria where you can taxi up to the door, Mount Rushmore, Grand Canyon, landing at Telluride (we did it partial panel in IMC - a good experience that it can be done).
I would fly in to some of the big airports en-route because it's fun.
I know you're on a budget but if you can rent an aeroplane with an autopilot I think it would make life much better, though with two pilots on board it might not be so bad. If the aircraft doesn't have a GPS I'd buy or borrow a decent handheld one.
Also, I'd echo what Keef said. I'd be tempted to start and end in California - most of the good stuff is out that way.
For quick "how long will it take" planning you can use
http://fly.dsc.net but once you're getting more serious I'd recommend
http://www.aeroplanner.com where you can plan your route on current sectional charts with all TFR's in place.