Two concrete tubs fed by a large pipe shower contraption just in sight of Interstate 8 and only a few miles from the Mexican border, Highline Hot Well is an experience. This is one of my most visited onsen in the USA because it was free and along the drive home from university at the time. The water is piping hot and can reach about 48 degrees from the well, but by the time it gets to your body it should be a little cooler. I do attribute my love of the 46 degree bath at Minatoyama Onsen in Kobe my many visits to this spring. The water has a somewhat metallic taste to it leading me to believed that there is a large iron content to the spring. Directly across from the spring is a long term camping area for RVers. There are two rather dirty pit toilets next to the parking lot that I would avoid if possible. People say they swim in the runoff pond behind the palm trees, but I never have and cannot recommend it. I also recommend using your best judgment when getting into the pools here. Sometimes in the off seasons in summer they get a bit dirty, thankfully the shower is always flowing good clean water. You will be more likely to enjoy the water by yourself if you go during the burning hot summers. The best time to enjoy the spring is during the monsoon season in August where you can enjoy a cold shower from the sky and a hot shower from the earth at the same time. Also be careful about broken class always wear sandals, slipping on the concrete, and crime. Always lock your car.