Sure, you could plant the trees there. I would plan on keeping them heavily pruned to the shape that best screens the neighbors while still fitting next to the wall, all while not letting them get too high. I would also plan on the pavers raising up eventually though keeping the tree size controlled to about 7 feet should jeep the roots on the smaller side. Were you set on the 2 varieties? Adding 4 different varieties can give you great tasting fruit for a longer portion of the avocado season. A fuerte would be good in there. The branches have a spreading habit so pruning would be a necessity.

Hi Renee (if you're still there) Just wanted to let you know that I followed your advice throughout winter, and my little tree basically just hibernated. But since the days have started getting longer again, the tree is growing like crazy! It's a very happy little tree now! Thank you for the good advice :) Sarah

If that was my tree I would spray it with a copper fungicide because from the picture it looks like a fungal disease. Avocado trees can be prone to this problem. Be sure to not over water the tree especially this time of year. I see that you are in 9b. You have the tree planted out in the open, not in a warm microclimate. At this size, avocado trees aren't very cold hardy. I also suspect that it got stressed from the cold snaps that we had in earlier in the winter. Check out my thread on cold protection with directions and pics on how to make a mini-greenhouse for your tree. It won't take much of a freeze to kill that young tree. You must protect it from freezes until it gets much older. If that is too much work, pot the tree up and bring it in the garage during freezes. Replant the tree in a more protected area. The best place is close to the southeast part of the house. Also, some of the remaining leaves have brown ends. Possible cause is over fertilizing. So next year, fertilize frequently but VERY LIGHTLY. It looks like the tree will recooperate if you give it the extra effort. Christine

Ginger, it looks to me that the soil is too wet. If it is outside and with the daily showers, did not have a chance to dry out. One of the most common problems in avocados is root rot. Try to move the pot to a drier place and wait to water till the mix is dry. Probably the leaves will fall by themselves, the brown is all the way up. If it does not get better, it might be a fungal problem. Silvia