Generally the best way to ignore the loop region is to do just that ... ignore it. There are really only two cases where it matters. There's a "loop playback" button under the timeline near the other controls. If this is on then Vegas will loop that region repeatedly while playing. Turn that button off and Vegas will ignore the loop. The other case is when rendering. In the advanced render screen there's an option to 'render loop region only'. Once again, with that turns off Vegas will ignore the region.

Other than those two cases, if you ignore the loop region and pretend it's not there, it won't bother you.

That being said, i too find it annoying to have those yellow triangles up there. It doesn't bother my editing at all, but visually i find them distracting. If you press i and then o without moving the cursor inbetween then the loop region's length becomes 0 and it has no effect. Sometimes i'll move the cursor back to the beginning of the timeline and then press i & o. That moves both triangles back to the left edge of the project, which is where they start out before they've been changed. However, none of that is necessary if you practice ignoring them.