Lots of kids like you today and a California choir kids group as well. Looks as though they were all enjoying the mission.
you can always take the train (metrolink) to get there, which is nice, in case driving isn't an option! but there's too much to learn about the mission that happens in person from seeing it with your own eyes while listening to the audio tour. also it's a good idea to do to guided tour, because whoever does that is an expert and can answer lots of questions for you! looking it up online is probably a better way to get info than asking people who've only visited. the online info is likely to be more complete and have photos! but just go, you'll be glad you went in person!
Sorry I am in Georgia so I don't know about the weather. The mission however is Awesome to go visit no matter what the weather is like. Use Groupon to buy the tickets for a big discount.
I'm back in Colorado now. We were just visiting. Very nice place to go. While we were there there was at least one school group there as well.
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