In my honest opinion, jQuery Mobile is not the best tool to use in PhoneGap based apps. jQM is dependent on jQuery which contains a lot of code that is not really required when you are building a mobile app. There is code in there that supports IE and Firefox but since the big three mobile phone OS'es (iOS, Android, BB) are all WebKit based it is just over kill.
However, if I was going to use jQM in my PG app I would use a single page approach if at all possible. This will prevent a couple of common issues that people see when using jQM/PG. For instance when you navigate to a second page the transitions are not always great on the mobile device, they are particularly bad on Android. As well when you app moves to page two it has to reload jQuery, jQuery Mobile and PhoneGap and this takes time. So if you can fit everything into one page by doing show/hide div's it would be better performance wise. If you need to go to a second page look at loading it via AJAX into the current pages DOM.
Also if you are on Android you may want to disable some CSS to get things to run smoother.
https://stackoverflow.com/a/8212384/41679