I'll immodestly recommend Soar Minden. We have about a dozen students
a year (or more) come from all over the world to do exactly what you
propose: spend a week of concentrated flying and end up with a glider
rating. Our weather is predictable and you could probably count on
flying the whole time you're here. If you come in March or April
you'll probably fly in wave, possibly even leave with an altitude
diamond. If you come in May or June you'll be flying in great thermal
conditions, probably including some nice cross country flying and maybe
leaving with a Silver badge. Take a look at our web site
www.soarminden.com for specifics on what we offer, or give me a call
at 1 800 345 7627. Fred