I agree with mnemosyne – it’s been my experience that learning English provides a foundation that you can use for a number of other styles.
It is difficult to become a highly skilled English rider, and this is just as true for becoming a highly skilled Western rider. Looking at a rider at the top of his/her form in either style, you’re seeing a very demanding and specific skill set. However, I believe it is easier to be a passable recreational Western rider (not easy but relatively speaking, easier) than to be a passable recreational English rider. Therefore, someone studying English will have a okay time of it if she spends a recreational day here or there riding Western, but not so much the reverse.
In terms of horse ownership, you can certainly ride English for pleasure and basic trail riding. Keep in mind that Western riding developed to provide specific skills for people who were working. I don’t know if your pleasure riding is going to require you to haul a cow out of a river by attaching a rope to the horn of your saddle . (And seriously, if this does interest you, it answers your question because you should then start learning rodeo) I have heard people claim that the larger Western saddle provides some protection for the horse on rough trails, but I have to say I don’t really see this, because it’s not covering that much more of the horse. I am pathetically East Coast-centric, but it’s my understanding that while 50 years ago there was a limited availibility issue for people looking to purchase English broke horses on the West Coast, that that is no longer true now. I don’t think that will be a factor for you, but you should certainly ask horsey people in your area.
For a beginner, it is more comfortable to sit in a Western saddle for a day-long trail ride, but I think the comfort factor is reduced the further along you get with your lessons.
Then there’s the whole neck reining thing. Western riding gives you the luxury of having one hand free, which is certainly nice, especially on the trail. Any decent English instructor will be able to teach you to rein one-handed as well, especially since you’re guiding with your legs in most cases.
Eek, I hope this doesn’t sound as if I’m slagging Western, I enjoy it myself and I would welcome the opportunity to learn more. Back in high school and college, I worked part time as an English riding instructor, and it always seemed to me that a good number of people coming from Western riding had more trouble mastering the basics of English.
My final recommendation is about your choice of instructor (and you didn’t ask about that so you might want to ignore me while I prattle on). I would definitely find an instructor who is going to give you the most rigorous training possible. Some people go into lessons looking to simply enjoy pleasure riding with the horse, and so the instructor provides easy lessons. I am firm in my belief that a student will only benefit from having the finer points driven home in the very beginning of the learning process. Even if you are riding very gentle, seasoned barn horses, your instructor should have you ride with the goal of being able to ride any feisty horse that you may encounter. It’s a lot easier to learn good habits than to unlearn bad ones. I’ve seen instructors tell students to ignore things like lead changes, but even if your trusty school horse knows the lead change better than you do, you should still go through the motions every time so that you are prepared when you eventually ride another horse.