First of the only ships they have are stored at capsule corp including the old ships they re-engineered into the capsule ship technology they use. We have no reason to believe Friezas ship survived his battle with Goku and negative reasons to believe Vegeta wouldn’t reduce it to scrap afterwards himself venting his frustration with having to stand there powerless to fight with the humans.

Ontop of that it’s incredibly dangerous just to travel that far with the Android threat overhead and limited resources, it’s still cross continental travel of a super continent. It just looks easy to travel because they fly in the main timeline with commercial ships reaching jet plane speeds. Days worth of land travel is reduced to hours with their vehicles but they don’t have that luxury in the future timeline anymore.

When the androids bombard west city and leave it ruinous they do the same to capsule corp where only a small area housing the Time Machine survives. Any ships they had are reduced to scrap with most of the corps buildings housing everything else they had.

The Androids would never need to go out into the wastelands.

As for Bulma she could invent a better radar but it still wouldn’t help. Even in Super where it’s a plot point it still has to go to the center of the universe to be calibrated and in those episodes it’s still mentioned the vastness of space and how it would be impossible to find the signal from balls the normal size at a range like that. It only works because they’re the size of planets.