I've never been out west to a np, but I will soon, and money for vacation is the issue. When my wife and I finally go for it, we will carefully plan the trip to avoid crowded places. To us, there's little diffrence between The Bronx and Yellowstone NP. We'll avoid Grand Canyon as we would any urban center.
Forestnome: When you go, check out the National Monuments, such as Lava Beds, Dinosaur, etc. These are run by the NPS, but get fewer crowds. The surrounding areas are less 'touristy' as well. The Rangers have more time & energy to spend with you, & the destinations are often just as attractive as the Parks.