Welcome, Janira! Thanks so much for taking the time to visit planDisney with your question.
Your visit is just a few weeks away! Any ticketed Guest is more than welcome to come and go from the park as they please throughout the day. You are also correct though that there is a chance that if you leave and return the park could be at capacity and you would be refused entry. I will say that this has happened in the past, but rarely. I've heard of it happening at Christmastime, but I don't think I've heard of it happening recently. So, yes you are welcome to leave and come back later in the day, but you do run into a small chance of the park filling up to capacity.
While I know plenty of people who leave to take an afternoon break, my family usually prefers to take a break IN the parks. At Disneyland Park, we will take a ride on the
Disneyland Railroad for a loop or two. I love watching other families enjoy the park and getting a different look at the park. We love snacks and mid-day we usually will find a good spot in the shade to sit down and enjoy some treats.
At Disney California Adventure Park, we love to cool off over at
Animation Academy. I could easily sit in the common area inside there and enjoy the Disney songs or get in line to draw my favorite Disney character. Across the way from there, grab a cold treat from Schmoozies! and grab a spot under the Hollywood Backlot Stage awning and then catch a showing of
Mickey's PhilharMagic.
Janira, hopefully, this information is helpful and gets you one step closer to your Disneyland Resort vacation! See you real soon!
Carrie