My husband, 3 year-old, and I visited Disneyland in May. It's the second time she's been there. The first time, she was 2. She was definitely more able to appreciate it this time.
Below are some tips on how to get the best experience for you and your pre-schooler.
1) Get a stroller first thing - Disneyland has these jogging type strollers with awesome maneuverability and it fit our big 3 year-old. We would have stolen it if they didn't have guards everywhere. You can also prepay for multiple days, which we did. On the morning of the second day, we just showed them our receipt and breezed away with a stroller while others waited in line.
2) Use Fast Passes - Many of the popular attractions have Fast Passes. Machines at the specific attraction will scan your admission ticket and give you tickets that show when you can return to skip through the line. There are limits to how frequently you can get the tickets. Many times, the timeframe they give you is way longer than waiting in line. Where we could have used it was on Splash Mountain. We waited 60mins - a lifetime for a 3 year-old.
3) Meals with Disney Characters - We did both the Minnie and Friends Breakfast and Princess Dinner. We called a month ahead to reserve a space. If they don't have room, you are S.O.L., whether you paid or not. Our kid loved both. She is really into Princesses right now. My husband and I enjoyed the Minnie breakfast more. If you have to choose, pick the Minnie breakfast and bring your kid to the Princess Fantasy Faire to meet the Princesses.
4) Tickets - We got park hopper tickets as we were there two days and the price was the same as Disneyland only tickets. The Princess Dinner is in California Adventures, so we needed it anyway. But if you are only visiting Disneyland and only for one day, the Disneyland only ticket is way cheaper than the park hopper.
5) Accomodations - We stayed at the Sheraton Anaheim, on the other side of I-5 from Disneyland. They charge $10/night for parking and have a free shuttle. When we return with my family and nephews and nieces, we will likely stay on Disneyland Hotel, but for just the 3 of us, it was not cost effective.