Road trip, places to go? and what about cost?

Me and some friends are planning a road trip this summer for about a week, were starting in San Diego and heading upstate to yosemite and back. Any cool places to go around there or on the way? we may want to back track around through nevada and down to the grand canyon. when would be the best time to go as well knowing gas prices will change. how much should we expect to pay for this? we'd be tent camping rather than hotels each night, possibly up to 10 people in 2 cars. also any good tips in general? ive gone on road trips in an RV before, but not car camping