East Bay Motorsports in Hayward is the closest Seadoo dealer I have dealt with.
I was happy with a dealer in San Mateo - but they packed up years ago. San Mateo was where I originally bought the boat.
GP Motorsports in on Camden in San Jose (not far from my place). But I have yet to take the GTX or HX in there since I do my own maintenance now.
Grand Prix in Mountain View isn't my first preference due to the difficulty I had with scheduling many years ago. And for a while they were selling Seadoos, then they weren't, and now they are again. But on balance, they did do warranty repair work on my craft.