I walk about 2 to 3 miles a day with a stroller but I'm worried if I bring my Boston it will be too much for him. I feel so guilty leaving him home. Is 2 to 3 miles ok for him?
Is he old or infirm? Some Bostons like to walk and others do not. As with anything new, start him out slowly, don't do it during the hotter parts of the day, and bring water. Unless he has respiratory issues because of his facial structure, he should be fine, so long as you are walking a normal pace and not jogging. Also, you might want to confirm this with your vet.
Based on my experience, 2-3 miles seems like a stretch, but it all depends on his cardiovascular health, age, disposition, etc. Boston Terriers are a brachycephalic breed, which means that their airways are more compressed. This leaves them at risk for exercise intolerance.