I have tried to grow a tomatillo and have had no luck with them fruiting.
Answer from Master Gardener:
Tomatillo plants require two or more plants for proper pollination. Thus, isolated tomatillo plants rarely set fruit. I have only planted tomatillos twice and found they required a long growing period to produce fruit. From the research I did, tomatillos require full sun (6-8 hours), ample and even moisture, at least two plants for pollination and 120 days to produce fruit. Most sources stated that tomatillos require conditions similar to tomatoes. A lot of people have the same production problem--lots of blooms but no fruit.