I have only had canned nopalitos. MacFrugals (like Big Lots) had them for a dollar a 1 lb 12 ounce can (794 g to the english-units-impaired) last spring. The taste is quite reminiscent of okra or green beans, especially in the following salad from the Embasa can:

Rinse and drain the cactus. Combine the cactus with the onion, tomato, cilantro, oil, lemon juice, vinegar, oregano, salt, pepper and cheese. Pour ingredients into a large salad bowl and sprinkle chopped pork rind over it. Garnish with tomato and cilantro adn serve. Add hot peppers if desired.

This salad makes an excellent taco filling, too.

I cannot vouch for the taco filling, but the salad accompanies a Mexican style meal very well.

There are some opuntia growing in Ozark glades south of St. Louis, Mo, but they are small. There are awesome (though a bit moth-eaten) ones on the road to Kula, Maui, Hawaii at about 1900 Msl. They would probably be a bit tough and would not do in the salad; the can label says it contains "Tender Cactus Nopalitos!"