English courses with horseback riding
A small number of language schools offer horseback riding lessons alongside English courses. Many of these are in Ireland, although there are a few in other countries. There's a wider range of options if you're a more advanced student and don't need English courses at all, but are just looking for an English immersion experience. In that case, there are working ranches in the United States, Canada, and Australia as well that will be glad to have non-native English speakers come and ride with them, for a fee of course. There are also a variety of summer-camp type programs that run in riding clubs and that are specifically aimed at international students. These are not open to adults and usually only available in June, July and August.
Practicing a sport you love in another language is an appealing alternative to traditional English courses. You're doing something familiar, the sport, but in an unfamiliar context. The language used for any particular sport is relatively limited, which allows you to gain mastery over that vocabulary quickly. At the same time, you're in a position of confidence and can perhaps more easily speak out and try your new English skills in the saddle where in the classroom you'd be shy. For the horse-lover, an English + horseback riding holiday might be just the thing. The schools listed below are a good place to begin your research.
Horseback riding in Ireland
Horseback riding elsewhere