L.R.
When you move, immediately:
Set ground rules. First with your husband himself. Does he consider himself close to his family? Does he plan to spend a lot more time with them "now that we live so close!" and very importantly -- has he defended you in the past and entirely taken your side when his family members have talked like this about you? If not -- HUGE problem. He needs to back you 100 percent. If he is going to let you handle them yourself, he is asking for you to resent him and for your marriage to be damaged. You and he have to talk about what it means for you to be living close to his family when you have these issues with them.
And set ground rules with him about family visits and expectations. Are you and he and your child going to be expected to attend every birthday dinner, holiday celebration, etc. all year? Will you be talked about and blackballed if you don't? Do you anticipate that the relatives will drop in unannounced? (That would never, ever work for me.) Again HE and you both have to agree on boundaries or there will be constant friction.
And for yourself: Immediately get out and find your own circle of friends. Whether it's at a new church or other house of worship; through a sport you play for fun; in a moms' group; anywhere -- find your own friends. You cannot end up just hanging out with the relatives by default. You must be able to say, "I'm going out this Saturday afternoon with my (whatever) club for an event" and your husband must be willing to give you that time. (And not just shove the kid at his parents or relatives to look after.)
Why are you making this move? If it's not for a very, very good reason, I would seriously question being in the same area as his family. Be ready to set boundaries and stick to them, but most of all, get him sticking up for you. And do find those friends of your own.