We have one sainted club in northern california that offers intro classes (both urban and field) but they are always full (they are VERY popular and very good) – www.sacramentodtc.org. One thing you might contact them about is whether they take auditors, because you can learn almost as much from just watching as from doing, at these classes.
The other thing to do is to drop into tracking tests near you to spectate, or maybe even see if they can use you as a worker/volunteer (that’s the way to get “front row seats”). At tests, you can see the sport in action, see and hear people talk about strategies and techniques, and get started with networking with the tracking community. That’s where you’ll hear about anyone offering classes or groups getting together to train on an irregular basis. If you are interested in doing this, contact the club offering the test and they'll hook you up with that test's volunteer coordinator. A pretty good list of upcoming tests is available at https://www.bumpsays.com/Home/tracking . Now, it turns out that the summer is off-season for tracking; urban tests don’t start until December and field tests don’t start until January. But you can have a look and save the dates!
There’s online instruction you can have a look at, as well. I’d start with https://www.fenzidogsportsacademy.com/ . In the off-season, you won’t see any intro classes, but keep checking – these fill up fast too. Huh, I do see they list an intermediate class starting in June (“Foundation tracking 2”) – I know you can sign up to just be a fly on the wall, for these classes, if you like, while you are waiting for them to offer “Foundation tracking 1” again! (By the way Fenzi is offering tons of nosework classes which aren’t tracking but do get the dog used to using their nose on command. It isn’t recommended to train nosework and tracking at the same time because they have some conflicting requirements, but it is VERY possible to train one and then train the other. The conflict is that in nosework the dog finds the scent without needing to know where it went before its final position; in tracking you don’t want the dog to skip the path to the scent – you want them tracking the path the scent took to its final position.)
Here’s some good general intro/info links to read up on tracking:
++ http://images.akc.org/pdf/events/tracking/beginners_guide.pdf .
++ https://www.akc.org/sports/tracking/getting-started/ .