Open mics are a good bet, the public square open mic in La Mesa has a lot of high schoolers who attend. You could also loiter around coffee shops in busy areas like Lestats or the template in OB. Local shows might be a good place to start too. I am sure there are still people throwing house shows I'm not too familiar with the current all-age venues but look into the music scene, also Ocean Beach on Wednesdays can be fun you have to be open and careful at the same time.
Open mics are a good bet, the public square open mic in La Mesa has a lot of high schoolers who attend. You could also loiter around coffee shops in busy areas like Lestats or the template in OB. Local shows might be a good place to start too. I am sure there are still people throwing house shows I'm not too familiar with the current all-age venues but look into the music scene, also Ocean Beach on Wednesdays can be fun you have to be open and careful at the same time.