I have found spider mites just covering some weeds and so now I keep them killed down regularly with a bit of Roundup; but that doesn't help with what my neighbors have growing. I don't think it is possible to remove all the surrounding sources of spider mites and they are so small I just know instinctively that they must blow in with the wind or rain. The best option is to remain vigilant and react quickly and decisively when you first see signs of them appearing. Most people around here just give up on their tomatoes around the first of July so there are plenty of host plants for them to breed uncontrollably on. Usually they aren't a big problem until after July and I am one of the few people I know around here that continues to grow through the heat of the summer so I just have to keep fighting them when they show up and they usually do.
Bill