Feria del vino fino
Feria's are held all over Andalucia and Spain. They comprise of two parts: A fair ground for the kids and a village of beer tents for the adults. Though you don't usually drink beer, but Fino which is a sweet white wine and an acquired taste! In other areas this is different but as the Feria of El Puerto celebrates fino it is certainly true of here. You also dress up in Falmenco type gitana dresses and dance Sevillanas which is a traditional dance from Sevilla (seville).
Horses are also a big part of it in Jerez and there is a parade down the main street though you can see plenty of jorses in the El Puerto feia just like you can drink plenty of fino in the Jerez feria.
You can mix the Fino with lemonade to make rebujito which makes for an altogether more enjoyable drink.
Each town holds their Ferias at different times though it kicks off in Sevilla usually in May though it varies depending on Easter. Next is El Puerto usually the week after.