Ear infections are caused #1 by moisture in the ears. Poodles are a breed that tend to grow a lot of hair INSIDE the ear which tends to hold moisture. If you groomer isn't plucking the hair out of the insides of the ears then you need to speak with them. If they don't do it then you'll need to talk to your vet about plucking the hair OR learn to do it yourself. It's not difficult, it's just uncomfortable for the dog for a few seconds. ALSO, when your groomer grooms make sure you ask them to shave the hair on the underside of the ear and if possible it's not a bad idea to keep the ear hair trimmed short in general (if you're not showing your dog).
Next, you can take a dry gauze pad and wipe out the insides of the ears occasionally to keep them free of debris and dry. You'd be surprised how far down you can get your finger and how much gunk comes out. Before you start your own regular cleaning like this however I would recommend that you have the vet clean those ears out well for you so you have a good start. If you have a great vet they'll even show you how to do it yourself!! There are solutions out there that actually help to dry out moisture in the ear canal, but in order to be sure you have one that will do this talk to your vet. Be very careful about putting any home remedy solutions in the ear. Not all of them assist in keeping the ear dry and that can sometimes exacerbate the condition.
Also, ask your groomer to be VERY careful about getting water down in those ears when bathing.
Some dogs are more prone to infections than others, and there are lots of things that can increase the number of infections (even allergies can cause increased infections).
Good luck!