Scwatk
Im not surea bout the Tahoe area as ive never fished there, my advice would be to go to some of the local fly shops and ask for advice. Usually for 20-30$ of flies you can get all the advice you want (much cheeper than a guide), start by asking where the fish are biting and what flies are producing. As for stoping in the mammoth are there are a ton of options. My favorites are hot creek, big springs and the san juaquin river. Hot creek is down the same road as the airport, its right off the 395. Its a fly fish only area c and r and barbless hooks. Follow the signs to hot creek geological area, this whole stretch of river has a ton of fish but they can be picky, an 18 or 20 caddis is your best bet. Big springs is past mammoth village if your going north, im not sure of the exact turn but the tackle shop guys will know. Theres not as much fish here as at hot creek and not as much fishable river but the fish are less pressured and can be easier to catch. Good patterns here are the caddis, the black and olive trico spinners, and the parachute addams. hope some of this is usefull let me know if you have anymore questions. Let me know how you do.
Dan