I live in a very warm climate (Phoenix AZ) and I was wondering what the best growing conditions (temperatures) are for an avocado plant? Are the extreme heat summers here to much for an avocado? We can also get about 4 or 5 nights out of the year where it falls to around freezing, will this be difficult on an avocado tree also?
The problem isn't heat so much as humidity. these trees love heat, and can take well over 100 degrees Fahrenheit without problems, if the humidity is high enough. The wind, sun and heat all dry the tree, and the humidity counters that. So You may end up with at best brown-tipped leaves (not fatal, or even a real problem), or in worse conditions, lots of new growth dieback each year after it dries out.
As for cold, it depends on variety, but usually they can handle down to 20 degrees Fahrenheit without burning.
Daily (or regularly, on a set schedule) watering will provide good growth, but won't compensate for low humidity. Avocados have large leaves, and let out quite a bit of moisture through them, in dry atmosphere conditions faster than they can take it in through the roots.
If you have a sheltered area (like along the north wall of a house, where the wind won't be as bad and you'll miss the afternoon sun), you may get better results. Other than that, you would have to alter the conditions, which is almost impossible outdoors.
I'd go ahead and get a tree, and try it out. Some plants turn out to be very resilient, but if it doesn't live, you'll know for next time.