What engine mods do you have? Premium should be fine with a 250 if it's a pretty mild build. 32/1 and klotz is fine to. Pump is more difficult to tune because of varying ethanol contents up 10%. Also ethanol is susceptible to water and deteriorates faster.

Where are you located doug? i'm in northern Michigan, they also sell rec. 87 and 91 ethanol free fuel up here to. I run 110 race fuel or 100LL avGas in all my quadracers the others get rec 91. I think on a stock bike you should be good with the rec 91. Get the squish cut properly on the head, when you freshen the engine, it is a definate improvement on reliablity and will be more responsive and less likely to detonate on lower octane fuel. If you start modding the engine to much, you will have step up to the pricey stuff fuel wise.

Deffinatly run the non ethanol. 32:1 is fine with good oil, klotz is fine. I prefer 927 but you will get seperation when its cold. Just be sure and keep it jetted safe.

you should be fine.  Just pay attention to your jetting from tank to tank.  ATV gas tanks are vented well and should ever accumulate water like a mower or weed eater would.