It's by no means 50% in my harbor, Santa Cruz, CA, but there are probably dozens in there. Lots 226/228, 232, Marlins, Expresses, Canyons.
It's kind of funny, at our beach cabin we used to call it an "Arima beach" because everyone owned an Arima, but now it's the complete opposite where everyone owns a Grady White. I've got my 228 Seafarer, the neighbor to one side of me has a 270 Islander, another has either a 235 or a 255 Freedom, and then the last neighbor has a 192 Tournament. Jacobsen's Marine is the local Grady White dealer in Edmonds, and they're the only one I believe for the entire PNW until you go across the border into Canada or go down to central California. There's a good deal of GW's around here but I don't think they're even close to 50% either as you've got a ton of Arima's, some Stripers, Trophy's and other fiberglass boats. Then you've got the aluminum crowd, which I've personally never been a fan of but people seem to love them, which would be Wooldridge, North River, Duckworth, Alumaweld and so forth. And finally you then tend to see a good deal of older boats from the 1970's and 1980's that are usually in very poor condition, which makes me wonder how they're still even running/floating.
For GW's specifically, most seem to be walkaround models but few of those seem to be 226's/228's, most are typically 208 Adventure's, 232 Gulfstream's and even the bigger ones. Occasionally you'll see DC/CC Grady's like the neighbors have, but those aren't quite as common as the WA's. Arima's around here are like a cult following as they were built in Seattle and now they're built in a place called Bremerton, which is about an hour drive from Seattle out on the peninsula. I owned two 21' Arima's before and they were great when the water was calm and flat, but goodness you'd take a pounding in them when there was 1'-2' chop and greater, which is why I sold those and bought my 228 Seafarer. It is always nice to see other Grady owners here, especially a 228 Seafarer as they aren't as common, I'll always give them a nod or a wave as I go by. I don't think that GW's will ever be as prominent out here on the west coast as they are on the east coast because that's where they're made, and most out here want a WA style of boat, which Grady more and more seems to be going away from.