Yes, two or more people can sync data between muliple devices. You do not have to share the same iCloud or Dropbox accounts.
Road Trip uses Dropbox for syncing data between devices. If you're not already a Dropbox user it's a free service and you don't have to install any additional software on your iPhone. Visit http://dropbox.com to create a free account, then sign in using Road Trip.
It's easy to set up syncing in Road Trip. Begin on the device that has your most recent Road Trip data:
Finally, repeat these steps on your other devices. Road Trip will now automatically sync with Dropbox whenever you add or edit data. You can also select Sync With Dropbox at any time from either device.
For full instructions, follow the link below.