Howdy, Chris! Thanks for stopping by planDisney!
I'm so glad that you are considering upgrading your
ticket to the Park Hopper option! You will definitely want to experience all the magic and fun that both parks have to offer! To upgrade your ticket, simply stop by a ticket booth at the Disneyland Resort and pay the difference between your one park per day ticket and a Park Hopper ticket. You will keep your
theme park reservation you had in place and then at 1:00 p.m., you can begin hopping to the other park. You can even hop back and forth between parks the rest of the day if you wish.
Since I see that you are visiting on
October 5th, I wanted to make sure that you are aware that the Oogie Boogie Bash – A Disney Halloween Party will take place that evening at 6:00 p.m. at Disney California Adventure Park. This party requires a special event ticket and those without tickets will be asked to leave the park at 6:00 p.m. If you had a theme park reservation for Disney California Adventure Park on October 5th and that's why you plan to upgrade to a Park Hopper ticket, then that's a wise choice! Because at 6:00 p.m. when Disney California Adventure Park closes for the party, you can hop on over and enjoy the rest of the night in Disneyland Park.
If you intended to start your day at Disneyland Park and then hop over to Disney California Adventure Park in the afternoon, just be aware that you will only have a few hours in the park before the Halloween party begins. I still think that the Park Hopper is worth it, especially if you're only visiting for one day, but I wanted you to be aware of this before making your decision.
I hope you have a wonderful time at the Happiest Place on Earth!
-Linda