Our Beagle mix is really hyper ( like most beagles) and when he sees another dog, he starts to bark & get all excited. Because of this, we have a tough time taking him for walks. He has never nipped or been aggressive, just really really excited when he sees one. So much so that the other owners get nervous & pull their dog away. We took him to training & he was perfectly fine with all the other dogs in his class... because he got to know them. The trainer suggested we allow him to go over to the other dog for a quick 2-5 second sniff to say "hi" but it's been tough to try to tell someone that "My dog's not crazy and will not hurt your dog, he's just really excited and wants to say Hi" I can totally understand the other owner's standpoint, as they don't know that my little guy is harmless, but that doesn't help him/us. There are also no "dog parks" in our area where he can play off-leash so I'm at a bit of a loss ( also we would send him to doggy daycare, but it's really too expensive)

That's a tough one if he is fine with the other dogs at his training class.
Teach him all the basic comands, especially sit and stay and when you take him for a walk make sure you use these commands at regular intervals, even if there are no dogs around you.
Then when a dog does come past, get him to sit and focus on you.
He will know that the other dog is there but with strict training you should be able to get him to focus more on you and a treat than other dogs.
He will know the other dogs are there but with a dog... food is king :)
Might help not to give him any food for at least a few hours before walks so he is extra focused.

It will be a quite a while before this becomes very effective but if you just try try try hopefully he will calm down :)

What really is making an improvement with our dog is taking him for walks in a park that usually has a lot of dogs in it. The more walks we go on, the more dogs he sees, and the more he realizes that he doesn't have to freak out and pull our arms off to get to them. The bottom line is, the more dogs he is around, the more likely he will start to calm down. Do you have friends that have dogs? Are there groups or events that involve dogs? Anything and everything helps.