getting to the beach from Jerez
Ok. To reach a beach from Jerez. Possibly the nearest beaches are around Cadiz Bay and El Puerto de Santa Maria is the nearest town being about 10 or 15 minutes by train or various buses. The bus network in this area has a web site with routes (Spanish) and maps - see if this helps?
Apart from El Puerto you can take a bus out to Costa Ballena / Rota/ Sanlucar / Chipiona etc for the sea.
Or you could take the train down to the sea at Cadiz city itself. There are trains that run without making to many stops OR there are local ones (called Cercanias) that shuttle between Jerez and Cadiz.
You can see some information if you look at this:
For example, you can get off at Cortadura station which is at the beginning of Cadiz city (or any of the others) and walk to the enormous expanse of beach called Playa Victoria. Takes 40 minutes as you cross the flat lands inland from the Bay that used to be covered with salt pans.
Jerez does have a good Flamenco tradition as you probably know already and stages an annual Flamenco Festival but this is held during the colder months of Spring. There is a Flamenco centre including library etc so for the serious students they have a place to study. http://www.centroandaluzdeflamenco.es/
You may be able to use that link to discover where the Peñas are. Of course the best Flamenco music tends to be spontaneous and rather late in the evening in some smoke filled bar or pena !