They can tell you where to take lessons and you can meetup with them. Most salsa dancers take merengue and bachata lessons as well and this group meets in different clubs where lessons are offered.
Cheers,
Margaret (I belong to the Salsa and Spanish Language Meetups in Toronto)
You could also check out these salsa instructors and their Web sites for lessons in merengue and bachata. Usually they offer workshops in merengue, bachata and cha cha cha. And you can also pay for private lessons where you'll quickly make progress with 1 on 1 attention or with your partner. It's more expensive but more intensive and if you're a quick study you won't be held up by people who can't even get the timing.