Most alfalfa is higher in protein than horses need. This is really only an issue if the extra ammonia in their urine is problem (say you have bad ventilation in your stalls), or your horse needs restricted protein for a health problem. They also tend to sweat more.
The bigger issue with alfalfa is some of the minerals levels/ratios aren't ideal. For most mature horses this isn't a big problem, and can be helped by the addition of an alfalfa-specific mineral supplement or ration balancer. The high calcium and magnesium in some areas (CA is notorious) can promote enterolith formation. When you say out west, perhaps you are in CA? If that's the case I would recommend either getting hay from out of the area, or staying with a mix of alfalfa with something else (grass, grain hay, etc).
As Peter, Paul, and Mary say, a dragon lives forever.
Yes, enterolith's are the primary concern feeding straight alfalfa, so my vets have suggested no more than 50% alfalfa for the forage part of the diet. Not sure what the latest research, but I think it traces back to our water as a few people put in water filtration symptoms to avoid stones...
But I also find that since it seems to really fatten them up, you wind up feeding much less which is great economically, but that's a lot of hours of boredom where I find they find other things to chew and destroy. I agree that certain batches of Bermuda are not popular, so I opt for Orchard grass.
I free feed bermuda so they can't complain about not having anything to eat all day, and supplement with orchard and alfalfa as a treat once in a while. I was free feeding orchard, but it disappears too fast!
Sometimes feeding the alfalfa is the best thing to do. There have been times where I've run out of grass hay and can't get more at a reasonable price, though I usually only have to do a month or two. Use a supplement to fix the mineral imbalance.
You can also consider other grass hays or oat hay. IIRC, the oat hay can be high in sugar content if that's a concern. We have a few more options up north than you do in AZ.
If you've got a really good hay guy, you can get alfalfa that's more stemmy and less leafy, which will have a more appropriate protein content for horses. The dairy farmers prefer the dark green leafy stuff that is a later cutting. Some feed stores are savvy about this, and others aren't at all.
If you are allergic to a thing, it is best not to put that thing in your mouth, particularly if the thing is cats. - Lemony Snicket
Everyone has pretty much covered it, feeding just alfalfa isn't ideal for a few reasons- one of which being that you generally don't want to provide a horse with free access to alfalfa. Most will get way too many calories out of that. I'm in CA and did lose a horse (who had grown up in CA on alfalfa) to a stone, so I'm definitely wary of feeding straight alfalfa out here. I feed an 80/20 Orchard/Alfalfa mix and love it, but it is also very easy to get here and I get it for a decent price (well, for California prices... $20 per 100lb bale). I'm not a Bermuda fan, but if it's not too expensive, I would rather feed some of that during the day than have them be getting nothing for a long stretch between meals of alfalfa. If the Bermuda is expensive and you don't like it as much, maybe up the alfalfa some, but keep some Bermuda in there so that they have something to eat during the day?
When I lived in Ca we fed half Alfalfa and half oat hay. If I had bermuda available I would feed half that no matter what the quality was unless the quality was a safety issue. If it was only a nutrition issue then I wouldn't worry and would feed it for fiber and to give them something to eat.
“If you are irritated by every rub, how will your mirror be polished?”