We are beginning to learn Android, converting our iPhone apps over.
There is a rudimentary editor for layouts in Eclipse, but it's not very good. Is there a visual designer that would be on par with the iPhone "Interface Builder" ?
AFAIK there is no such builder yet for Android,
Check out droiddraw and try to make the most out from Eclipse builder, those are the best and only interface builders. Anyway once you get in, you won't spend to much time creating lots of interfaces, as you will reuse them or the inbuilt components like preferencescreen.
When developing and thinking about layouts, think them as they were like HTML layouts.