I'd rather go to San Diego Zoo than Disneyland. Mostly because I remember Disneyland sucking compared to Disneyworld. But I'd also rather spend time in SD than LA, so maybe I'm not much help.
I second this. Even though I really enjoyed Disneyland (never been to Disney World), I really felt like the San Diego Zoo was a much better value. The tickets are 1/2 to 1/3rd of the price of Disneyland, and you can actually see and enjoy the entire Zoo in one day. Also Red Pandas! Giant Pandas! An Ocelot! Koalas! Baby sloth!
We just generally fell in love with San Diego over the 3 days we were there. The atmosphere and the culture and the climate... I highly recommend The Neighborhood for food/drink in SD. The fried chicken deviled eggs sound odd but they are one of the best things I have ever put into my mouth. My husband and I both still dream about them.
Just some recommendations for Vegas... I do not recommend the Flamingo. The location is good, but the service is horrible (they double charged us several times and then the manager insisted that they hadn't made a mistake). Also, the ARIA breakfast buffet is a bit on the spendy side ($20/person) but it is also some of the best food in that price range on the strip that I have had. Its not something for every morning if you're on a tight budget, but I highly recommend it if you can afford it. Plus if you go just before 11 am, you won't have to eat for the rest of the day, so really you'll be saving money.
I wouldn't bother going for lunch or dinner though.
Hash House-A-Go-Go is another place to eat at. There's one in Vegas, but I believe there is also one in San Diego. Delicious, and a definite value for money - five of us went for brunch (including 3 hungry men), we ordered 3 plates to share and the 5 of us couldn't finish the food and it wasn't for lack of trying.
Vegas is great because there are lots of things to do for all budgets. Definitely check out the CBS and NBC Television Research Centers (in MGM and Excalibur, respectively), where you can watch/rate up-coming TV shows. The conservatory at the Bellagio is really cool and changes from season to season, and the Bellagio Fountains are really cool.