Hi, just curious, is this the same sprinkler group you referred to in past posts? The company that was replacing all the heads for the HOA. If so, suggest you find a new company to do your work. I would have trouble trusting them taking out the trash, from what you have described.
You sound like you have an interest in horticulture and in irrigation. That is what led me into the field. You probably know about Jess Stryker's site
http://www.irrigationtutorials.com/, but if not, it will keep you busy for a couple of nights.
Arizona has a great Master Gardener program. Great place to learn about basic horticultural practices, as well as general information to answer some of the questions you have posed.
Please accept my comments as I intend them, helpful not preaching.
Jeff