Fermenting just a few degrees above a yeast strains optimum temp will not generate detrimental effects, but you could lose out on the bread and butter a particular yeast strain provides. 2112 from Wyeast can stop providing lager characteristics once the fermentation temp has surpassed 65F. With a 70F ambient temp, and keeping in mind that when fermenting your beer's temp will increase 1-2F, that puts you at 71-72F. I would say you are defeating the purpose of using 2112 at that point.
I would highly encourage you not to ferment outside. Unless you got a cooler large enough to fit your fermenter, in WI you would be talking temp variations of 20-30F throughout the day. This is not good.
If you are going to get a different yeast, I would suggest making a 'different' beer.
Alternatively, I would explore ways to control your fermentation temp indoors. One way to do this is to use a wash tub (or a 'keg' bucket), place your fermenter inside, and fill the rest of it up with ~60F water. The water will not only keep your fermenter cool, but act as a heat sink so your fermentation temp will be very slow to fluctuate in the 70F environment.