I'm in Arizona rather than Nevada, but there might be some species here that might be usable, you know?
First, there's this list of plants of the Sonoran Desert, and it lists plants by family, so you just scroll down to the Fabaceae family to find legumes there.
http://en.wikipedia.org/wiki/List_of_flora_of_the_Sonoran_Desert_Region_by_common_name
Obviously, many of these are not going to work. They can take the heat, and although you get a little less rainfall (most of these plants grow in areas where there's between 8-12 inches of rain), there's less evapotranspiration where you are, I believe, so they might do okay, rainfall-wise, but the cold is going to be a bit of an issue.
However, many of the varieties grow up in mountains as high as 6,000 feet or more, so they can take more cold than the others, obviously. I'm not sure all of WHICH of the varieties that applies to, but they might be worth checking out. There's a few I've noted down, though (looking for ideas for my folks in the Rockies).
The one edible legume I know of that you might be able to use is the Velvet Mesquite (Prosopis velutina) - it's a tree that can grow up to about 25 feet, with about a 25 foot diameter canopy, a legume, low water use. Grows native in Az up to 6,000 feet in elevation (so it might be able to take your cold), but can also take temperatures that exist in Phoenix, so I believe as high as 120 F, in some cases. The pods and seeds are both edible, usually ground up to gather and used like you would use cornmeal. Sweet tasting. It's the only native edible legume in AZ that I know of which also grows this high. Palo verde, the other edible legume tree around here, only grows to about 4,000 feet, usually.
Featherplume (Dalea formosa), a legume shrub which grows at up to 6500 in elevation. I understand this one is supposed to be medicinal, as well.
Whiteball Acacia (Acacia angustissima) - legume, shrub, grows up to 6,000 feet. Butterfly larval source, bee nectar source.
False Indigo Bush (Amorpha fruticosa) - legume, shrub, grow's up to 6,000 feet, butterfly larval source.
California false indigo bush (Amorpha californica) - legume, shrub, grow's up to 8,000 feet, butterfly larval source.
Those are all the local ones I've researched and found at higher elevations (but I haven't gone too far in my research yet).
Also, just for AZ plants that might be of interest in a desert permaculture project that I don't see mentioned all that often.
Saya (Amoreuxia palmatifida) - AZ desert plant where the entire plant is edible, including the tubers.
Pineland Gooseberry - AZ native, but good up to 9,000 feet elevation.
There's also a few AZ native wolfberries (edible, related to Goji berries), like the pale leaf wolfberry (Lycium pallidum) which is good up to 6,000 feet
Good luck - hope the project goes very well.