@netrobot: Locus caches as much as you tell it to. When you go to download a map, you can select a variety of outer boundaries for the map (this screen, select area, by state, etc.), and then you can select which zoom levels you want to have access to off-line. I usually go for one broad view, one medium zoom, and then one or two finer zoom levels, depending on what I'll be using the map for.

A fast way to get the map out of Czechoslovakia, if it should happen to end up there again, is to have a 'user map' defined near where you most often need your maps. Then, you just push menu>user maps>'name of map'>center on map. Done.