You'll have to delete all of those interior paths, if you want to be left with a stroke only on the outside. You might want to consider using a different font, so you don't have to do this. But here's what I would do.
- select the text
- duplicate it
- Path menu > Union (converts to path and combines all the letters together into a compound path, in one step)
- add a stroke to the duplicate
- remove the fill of the duplicate
- zoom in quite a lot, so that one letter fills up the whole screen
- using the Node tool, select large chunks of the interior subpaths/nodes (for example, on an "i" or "I", you could select the whole column of paths, by dragging a selection box)
- delete
- repeat until you've removed all the interior nodes
In the end, you might want to group the duplicate (or stroke object) with the original, so that they don't accidentally get separated.
