I would say that the best way to answer your question is to visit Legoland's website so that you can get a clearer picture and description of the rides that they offer and then you can judge for yourself.
For a quick answer, their rides are good and yes, adults can ride them. Most of the rides are geared towards little kids but they do have some faster rides. Still nothing like Space Mountain or anything at Magic Mountain but it's still fun.
Again, check their website because Legoland in San Diego also has a little water park that kids enjoy. I know my kids love it. They also have a Pirate Bay area which is a water play area with some water rides too and my kids love that area too.