The sun shines bright in CA all winter long. I was wearing shorts and a T-shirt at the G&O garden railroad in the SF Bay Area this morning.
Those of us who live in the West are much more car oriented than we are public transportation oriented. Therefore, fewer people out here take the train as a percent of the population. There is simply more model railroading in areas where people ride and see more trains. Another factor, at least here in CA, is that good weather keeps people outside year around. This is why garden model railroading is very popular.
Although none of our train shows can compare to York, we do have more than enough train shows to keep us busy. O Scale West is the first weekend in February in Santa Clara (near San Jose - SF Bay Area). There will be some very nice layouts on the tour schedule. The Northern CA Cal-Stewart show is 22 March in San Ramon (SF Bay Area near Oakland). This is the big Northern CA TCA show. The Cal-Stewart show will have layout and collection tours for the first time this year. The Southern CA Cal-Stewart show is in October each year in Ontario (near LA).
This year, 2015, the NMRA national convention and the national train show will be in Portland, OR in August. This should be a terrific convention. I am planning to attend.
The Coast Division of the NMRA is having its local show in April. Next year, 2016, the National Garden Railroad convention will be in Santa Clara (near San Jose - SF Bay Area). Nearly every year there is some big train show / event at the CA State Railroad Museum in Sacramento.
When I was living in the LA area a few years ago there were a couple of trains each year at the Pomona fairgrounds. The City of Fullerton held a railroad fair every year.
I think you could keep busy attending a train show somewhere in CA every month if you wanted to spend your time and money doing it.
Joe