That kind of depends on how much you like driving, and if you want to do some sightseeing, too!
It's a LONG way from LAX to Monterey (~350 miles), so I wouldn't advise that unless you have some extra time (a day each way!). San Francisco is about 100 miles from Monterey, but traffic can be pretty bad in the SF/Silicon Valley area. It'll be easiest if you can fly directly into Monterey, but if you want to do some sightseeing in the San Francisco area then flying into SF would give you the opportunity. Flying into San Jose would be another possibility - that would be closer to Monterey than SFO.