Q. Do you have recommendations/suggestions for new avocado and lime tree plantings for Las Vegas? I currently have a Meyer lemon tree which is doing great.
A. I don't like to recommend lime or avocado for this climate, particularly avocado, unless you have a very warm spot in the landscape that can give off a lot of winter warmth and protection from winter winds.
These plants are very tender during the winter here and the chances of losing them due to winter cold is extremely high. That being said, if you decide to move ahead with a lime then any of the limes would be a good choice depending on your preference. Rangpur and red limes, although cold hardy, are not limes at all but could be used as a substitute. To my knowledge there is little difference in the true limes abilities to make it through the cold here so that would not be a consideration.
As far as the avocado goes, I would select a smaller selection to give it a better chance of surviving. Make sure the rootstock is also cold tolerant or you could lose the roots while the top did not freeze. Here are some recommended cold hardy varieties from a Texas website: http://toptropicals.com/html/toptropicals/articles/fruit/varieties_avocado.htm
Cold hardy varieties:
Brazos Belle: Produces medium-large, purple-black long fruit. Season: October-November.
Fantastic: Produces green, paper thin skin, supposedly the most most cold hardy of all. The fruit has a creamy texture.
Joey: Selected by Joey Ricers in Uvalde, Texas (just outside of San-Antonio). Produces medium size, egg shaped purple-black fruit. It has excellent flavor. Heavy bearer. Season: September-October.
Lila: Produces medium size, green fruit. Season: September-October. Don't confuse this variety with Lula, which is popular Florida variety and commonly used for rootstock. (Lula is cold hardy to 25F)
Poncho: Produces medium to large green fruit. Cold hardy to 15F