Hi Dpriceva and welcome to our forum!
Yes, in the InfoPath Designer you can add a SharePoint data connection that populates a dropdown from this SharePoint list. However, if it is really long, there are two issues: 1) the view may restrict it to 100 items (default), so you have to change the SharePoint default view properties to be large enough to show everything; 2) if it's several hundred or thousand items, performance could be affected. In this case, I'd move the data into SQL and use a Web service to filter.
We have a prepop tool that takes an Excel spreadsheet and generates XML files from it. If this is what you are looking for, please send me a private e-mail. We are in the process of making this tool available, but it isn't in our Downloads folder yet.
Cheers!