jllawson,
first of i wish you much luck in your hopes to become a 'spaniard' in whichever region you ultimately choose. the making of jerez is quite common in average households, and i doubt you'd have much trouble in acquiring knowledge of this in random wine stores around madrid, as well as conversing directly with your neighbor... it seems like every household has a cask with aging jerez in it...
others have suggested rioja, and south/southwest of sevilla as great wine regions. i suggest castilla-la mancha, if not only because it is spain's most diverse wine region, but also because it is inexpensive and the people are most friendly... of course, it could be that i am biased!
i recommend valdepeņas, manzanares, la solana, daimiel, vllnva de los infantes, albacete, toledo, etc... for wine areas of castilla-la mancha. i worked on a family vineyard in vllnva de los infantes and really enjoyed it... normally, gypsies do the actual picking of the grapes. i helped to put the grapes into the presses ( the same ones we use for olives ), and then monitor their fermentation in the tinejas(giant clay vats)...
you will most likely be volunteering, if you
decide to go into 'winemaking.' many
vineyards are either family owned, with
plenty of help a phone call away, or part
of a co-operative, again, with help a phone
call away. many indulge tours, but with
notice only. they will also offer wine
tastings if you ask. talk to 'nuestro padre
jesus del perdon' in manzanares. they are
quite amicable and will receive you, often
even same-day. also, bodegas Felix Solis
(of Valdepeņas)
will receive you on a tour; call for times
and days. this bodega is a family friend
of mine too. of interest, Valdepeņas used
to have the most bodegas of any city in
spain. most have gone bankrupt; a shame.
winemaking is not only an art, but an experience! i hope to retire someday into winemaking... maybe i'll be making wine in the same bodegas where i learned in twenty-five years or so... in any case, i wish you
luck in your pursuit of wines and sherrys!
good luck!