texas_girl,
Here is what I would suggest:
- Plant an avocado seed in the location where you want to have an avocado tree. Make sure the soil is fairly well draining (break up / amend as necessary). If you can find a Lula avocado (which are grown commercially in Texas) that is the best. Lulas are salt-tolerant and very vigorous. Actually the AZRFG chapter is trying to acquire some Lula seeds and if they become available, I will ship a couple to you.
- After the seed has sprouted, you want to keep it watered and provide some afternoon shade (if it ends up sprouting in summer/fall). Definitely baby it with partial noon shade and full afternoon shade if the temps are above 90-95 F while it is a seedling. On the flip side, also certainly protect it from the cold (keep it above freezing with either frost cloth or heat lamps / Christmas lights or both).
- After a few months the seedling will be a foot tall or so and be about pencil thickness. This is the perfect size for grafting
- I have an Aravaipa tree and can send you some budwood. Actually my tree is not doing great at the moment but assuming I can nurse it back to health I will be able to send you some budwood. You will want to do either a cleft graft if you can match up the calipers low on the stem or a veneer graft if the diameter mismatch is too great.
The Aravaipa is supposed to have a good cold tolerance, but I do not think anybody really knows how much it can take temperature wise. There is a report that the mother tree has had snow on it on suffered no ill effect. What is your USDA zone?