Hi Lois,
Yes, you can backup your database before you do the factory reset and then import it into the app afterwards and not lose any data.
From the main screen in Tumble Tally click Menu-->More-->Backup your Data
After that go into a file manager application and find the file and send it to Dropbox. I backup my Tumble Tally database this way all the time. I use File Expert HD for a file manager.
The database is located on my sdcard, so in the File Expert HD app I navigate to a folder called com.flintcreekapps.tumbletally\backup\ and the database backup file is named tumbletally.db
I select the file by checking the checkbox-->click menu-->Send Files-->Share-->Select Add to Dropbox-->navigate to the folder in Dropbox and click Add
Your file should get uploaded to Dropbox...log into Dropbox.com to verify.
I hope this helps.
-Mike