Well, there are a lot of options you can take. California is so unique in that it has cities that each have their own personality and great things about them. Also, the countryside (Napa, Santa Barbara, Route 1) is amazing also.
San Diego - amazing weather, fun bar scene, smaller town. Not too many all-male hotel choices, but good other elements. Black's Beach in La Jolla is one of the most well loved gay beaches anywhere
Los Angeles / West Hollywood - more a scene for the pretty boys, all that comes with Hollywood - meaning some great restaurants and attractions, but it's big and you have to travel around a lot.
San Francisco - gay central, amazing food, fun bar scene - for all types of boys and men.
Palm Springs - gay resort town with clothing optional resorts (and more calm ones too). not much of a restaurant scene.
Wine Country: Napa is only 1 hour north of san francisco, great wine/food - easy to hook up to a trip there. Santa Barbara is a 2 hours north of LA - also great wine/food
Depending on the time of year, you could do a few days in Palm Springs, and a few days in San Diego or LA. Or do two cities: San Francisco / LA of SF/San Diego.
All depends on your taste.