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Coming from the Balkans, YL is going to be very hot this summer and into late fall/autumn. The beach will be your friend all year. Look into an app called Groupon and get yourself some surf lessons with a friend for cheap.
Orange County back country is spectacular so explore the place with the All Trails app. Your host family will help you navigate most of it but learning to move about independently in a foreign country is half the fun.
Good luck amd stay safe :)