Plan for traffic & jerks, prepare for high gas prices & a fair shake of some hot gals n guys. lol- depending on where you're from it might be some strange sights in LA or interesting or amusing...lol here is A LOT to see, do, experience & eat in LA. What type of trip are you looking to have? laid back n chill, full to the brim with physical activities, mentally stimulating museum heavy, sight-seeing, thrill-park visiting, sports parks, etc? Here's a link to things to do in LA for May this year that might help you peruse the offerings:
http://www.thingstodoinlosangelesca.com/All-Events/13-May-2012/Popularity/ I'm sure once you're at the May page, June can't be to hard to find. Bring warm to hot (70-90 degrees) weather clothes & maybe lightweight pants & a light jacket just in case we are getting the June-Gloom (50-75 degrees, overcast, sprinkles occasionally & cooler AM w/warmer PM) & cooler evening temps, esp if you go to the beach or mountains. Have fun! Oh & do not depend on public transportation in LA, it blows...although the MetroLink isn't too bad overall. The problem with LA is it's spread out, not concentrated, but we have a bunch of highways (free!!! do not get on the toll roads tho, not free or cheap). Do get a map & not rely too heavily on GPS, while driving the freeways try to listen to the traffic reports, it can save you a headache.