Hi! Can someone tell me when the flamenco festivals are that take place in Sevilla and Jerez? Thank you!

In Sevilla, a bienial de flamenco happens on even-numbered years from about mid-September thru early October. So the next one will begin in September, 2006.

The Flamenco Festival of Jerez takes place in 2006 from the last week of February to the 10 of March. You can still see plenty of flamenco in Jerez outside that period.