4 year old needs help with dog aggression

Question
My 4 year old Boston Terrier mix (17lbs) is aggressive toward other dogs.  She is great with the two small dogs she lives with, but doesn't like other dogs.  When we see other dogs on walks, she becomes very tense, her hair stands up, and she some times barks, growls, and/or lunges in the direction on the doggy stranger.  Since getting a gentle leader (the face sort), she does much better, although she hates wearing it.  I am hoping to get her more comfortable with seeing other dogs on walks, but I would really love for her to be able to go to a dog park or doggy day care.

Any tips and suggestions for socializing my adult dog?

Answer
Sometimes dogs who are reactive on leash are better in situations where they have more choices (off leash) and some dogs simply aren't interested in interacting with strange dogs. A really good book to read is Emma Parson's "Click to Calm" and here's a link to an article with some ideas on working with reactive dogs. On the part about harnesses, I was actually talking about using a step-in harness with two points of contact (which allows for much better control (have a look at "Getting in TTouch With Your Dog" by Linda Tellington-Jones
http://dogs.fox10tv.com/Conduct/rehab_your_reactive_dog/index.html
Sandy Case BFA MEd CPDT www.positivelycanine.com