We just spent a week out there - 5 nights at GCH, two nights at the Hilton La Jolla Torrey Pines near San Diego. We left Disney and went straight to
Legoland, and that took a bit over an hour.
We chose to rent a car. We only spent three days at DLR. The other days we spent exploring the LA area/Legoland/exploring San Diego. If you are just wanting to go straight to Legoland and straight to Universal, like the PP stated, there are shuttles. But you may find that taking the shuttles end up costing as much as a rental car! We just rented a minivan for an entire week from Alamo for just under $400. It would probably be best to do the math!