You should be ok with sand and clay. I've never had any trouble growing figs in heavy red clay. Just add a few inches of compost in the spring and a few inches of mulch in the fall and your soil will be great in no time.

3 feet seems way too close. I've seen celeste's in my area with trunks at least a foot across, branches 20+ feet in all directions and thousands of figs. I would opt for 4 larger trees rather than 24 smaller trees. Larger trees are going to be more cold hardy.

I currently only have 2 fig trees. The first is a chicago hardy which I have about a 15' x 20' area for and plan to let it grow wild - except for keeping to one trunck. The second is a celeste about 6 ft from the south side of my house. I am shaping it like a Menorah and have about 15' in both directions set aside (plan to let it be 30' across by about 4' in depth). Except for the basic Menorah shape I plan to prune all branches each year.

Sounds like you really need a bigger yard. If you plant them with only 3 foot of spacing, this only leaves the tree 18" of space to grow from the center out before touching another tree. Your only possible chance would be to train them. Look up espalier training. Even with this, you will be limited but it's possible if you have a good imagination.I have not attempted this yet, but plans are in the near future. Good luck and hope you find a way.

luke