It's a long ride from LAX, about 45 minutes, and since we always stay offsite, we rent a car. We usually pay about $180-200 for 6 days. For us, it's a must to have a car there, as we go to area restaurants more than DL restaurants.
You might check out www.mousesavers.com. I've taken the bus and Super Shuttle. I don't recommend the bus; it's long, boring and can be very uncomfortable (we once had a bus with a broken overhead window and it was freezing!). Supershuttle has been OK. Car rentals weren't the best choice for me because there were usually only two in my party, we were only going to DL, and there was often a daily parking charge at the hotels we were staying at. The best choice for you could depend upon where you are staying, how long you are staying, and how many there are in the party. I'll always fly into Orange County unless I can get a much better fare into LAX.