Hi Devin,
I was able to do a little reasearch and was able to change the the currency format by adjusting the Window's currency settings. In Windows 7, Go to Control Panel > Clock, Language, and Region, > Region and Language > Additional Settings > Currency.
Form there, I modified the currency sign, the decimal symbol to a comma instead of a decimal point, and digit grouping symbol to a blank space. The only problem here was Infopath was not accepting the comma and instead wanted the decimal point. So the solution I came up with was to use a translate formula in order to change the comma to a decimal point:
translate(., ",", ".")
What's happening here is that Infopath will read the comma as a decimal point but will chage back into a comma because of the modified currency format at the Regional Settings.
Note that the field's data type is Decimal with 2 Decimal places. Hope this helps.