I would recommend just planting 1 or 2 plants per post. Plants need to attain a some mass to them before they fruit, it sees (and based on reports of very experienced folks), so planting too many together has them all competing for the same resources. I've gone to the pitaya festival two or three times. It's a very good event.
Many or nearly all pitaya seem to either require cross-pollination or fruit better if cross-pollinated. Most growers hand pollinate flowers every night. A friend of mine who is a commercial grower in north San Diego County has been breeding his own varieties to attain ones which are self fertile. He has a long history in breeding (an avocado carries his intials, GEM) and has worked with thousands of seedlings.
Pitaya fruit more prolifically if grown in more sunlight. Some varieties, particularly those from Guatemala, are more sensitive to sunburn and growers often grow them under 15% shade cloth. However, even this low amount of shading greatly reduces fruiting. Another husband and wife grower team (near the other one mentioned above) use shadecloth over their "G2" plants. Plants on the border of the shade structure have a lot of sunburn but maybe 50% more fruit than the same plant which is shaded on the other side. I think something like the Surround product I suggested previously for protecting fig trees growing in very hot regions may be helpful for such pitaya. Some, such as those that originate from Nicaragua, can tolerate full sun much more easily. These plants usually have a dusty white appearance. Some people like the Nicaragua varieties. Even though I have a close connection to Nicaragua (my wife and I sponsor three children and their families there and have been there four times in the past four years), I don't like them as well as they are not sweet enough for my taste.
I don't have cuttings to share because of cold damage but would suggest growing ones such as Halley's Comet, Delight, Physical Graffiti, American Beauty, Purple Haze, Natural Mystic. Some of these might be available on eBay or other sources. Pine Island Nursery sells them also. Many of these varieties were developed by Paul Thomson, the late co-founder of the California Rare Fruit Growers and big advocate of pitaya. Delight is the only one he named. The others were left with designations such as 1S (S for seedling) and then Pine Island came up with rock music themed names for them without giving credit to the person that developed them which I think stinks. Dirty rotten scoundrels! :)
At Irvine no hand pollination is performed and it seems that, for the most part, production is still pretty good with bees cross-pollinating the plants pretty well because of the sheer number of plants being grown. Bees do eat the pollen, however, so there needs to be plenty of pollen available.
Pitaya flowers are beautiful but open one evening and are wilted up by late morning the following day. Most have a very nice fragrance.
Here is a GIF I created from a series of time-lapse photos a couple of years ago.
Now, knock off this distraction from figs now, okay??!! LOL