hi baney, welcome to the board.
actually, although you posted this in the "off the beaten path" forum, yoga has become quite mainstream in madrid, especially amongst the ex-pat community,
a
SEARCH on "yoga" will do the trick.
check the threads for leads and also check the InMadrid classifieds at
www.in-madrid.com/classifieds, do a search on "yoga" and a few ads come up.
i also suggest you pick up a copy of the InMadrid newspaper as there are quite a few yoga centers that advertise there.
as for getting together, we do quite a bit. see the "buddy up "con" other travellers" forum. there are a few sports threads and one entitled "Sport Activities Summary" that lists all the sports that the mm-ers play.
you can also start a new thread on the "buddy up..." forum at any time proposing an excursion, i am sure that if you took the initiative other board members and lurkers would join you
saludos,
jer...