I worked in Yosemite for 18 years and here's the deal. The workers at Yosemite are in the union and jobs like server and bartender are awarded based on seniority. My best advice is to get a job in the Anwahnee itself and make yourself known to F&B management there then wait and see if you could bid on a position like busser. If you become busser than in unit seniority trumps all. Good luck.
That hotel is a premier historical hotel and very sought after. The suggestion that Stephen said is right on. The short time I worked in Yosemite that's all I seen is people that constantly vied for a position at the Ahwanee. good luck. It will probably take some time unless you either get very lucky or know someone.