I plant corn in early July in zone 5, for fall harvest. I would think that you'd do even better in your zone. I've also planted beans late like that for a fall crop. I would think that since you've got the number of days to harvest putting you well before frost, you'll be fine. Things will grow slower with the shorter days of late summer, though, so add some days to harvest time for your second crops. You've made a good choice between beans and corn, with a nitrogen fixer preceeding a heavy feeder, and vice versa. But you probably knew that already :)

Your grandfather is right. If you were to go out before the sun hits the plants and wash the frost off with a hose there would be no damage to the plant. We have had frosts when my strawberries were in bloom and I did spray them with the hose and those flowers produced berries. I am not an expert by any means and I'm sure someone has a scientific answer as to why, but like your grandfather I have seen from experience that what he says is true. As to the bacon fat--well there are a lot of old wives tales. Some are good, some have a smidgeon of truth and some are complete hogwash.

Last time we had a frost like what's predicted tonight after I had sprouts, I dropped a plastic tarp (actually a couple of painter's plastic drop cloths from Home Depot 'cause they were cheap) over my whole wintersown area. I pulled it off the next morning before the sun got too high and all was well. Two years before that, we had a very late March snow and heavy rain. That year I went to the trouble of actually putting a couple of sawhorses around the edges and draped the drop cloths over them as protection for the whole area because I had a lot of containers with sprouts. When I only have a few containers with sprouts and a frost is predicted, I moved just those containers into the garage and back out again the next day. I don't know if any of this was really needed, but I figured better safe than sorry. Any one have a less intensive response that worked?

I don't think Las Vegas is that much colder than Pasadena where I am and I planted my first roses here in December last year. The ground here never even gets that cold and they grow right from the start. I imagine your soil is as bad as mine is so I would work in as much organic material (compost) as you can and pile on mulch. And by all means fertilize with organics. I have two barrels of steer manure in water only because I haven't been able to find alfalfa. They love the steer manure. Also I would think that if there was ammonia you would smell it and if you do I wouldn't use it. I have never smelled it with any king of organic concoction I've used.