Wise advice yosemitefaerie :)) Visiting your in-lows instead of waiting for them to pop up in your house is very clever! I may use it as well :) And serious discussion about privacy with your husband could help also. You may tell him that your mother will come visiting you as many times as the in-laws and he will find a way to deal with the situation really quick :))))
I know how you feel, I was initially quite irritated with my in-laws since they stayed really close to me (like 5 mins away). Thankfully, they don't come over as often since we don't have any kids. What I do is I just say that I am busy or that I'm not home and they will leave me alone. But I don't avoidance will work in the long run. Just be tactful, and speak to your husband about the issue. You could also choose to go visit your in-laws instead of the other way round. This can put you in control of when you can leave for home or when you can come, because we all know we can't ask guests to leave!
If your in-laws are coming over too often, you can't totally cut them out of your life because that could sour relations, especially between your spouse and you. Instead, tell as the others have suggested, discuss this with your spouse, and tell him that you can only deal with his parents coming over at a less frequent basis. You don't have to hurt their feelings, just say that the both of you are busy for example.
Have you tried talking to your spouse about how you feel? Harboring negative feelings about your in-laws won’t be good for your marriage. You should also try every way possible to develop a sense of tolerance toward your family. If you just can’t get over your feelings, then talking to your spouse may help. They may be defensive about their family, so try to focus only on how you feel and not blame your spouse’s family for causing annoyance. That will only create a rift between the two of you, which could later be exploited by your spouse’s family if things aren’t going well between you.