In my experience working with native Spanish and Portuguese speakers both as a soldier and civilian, I am more comfortable dealing directly with them with my 3/3/3 Spanish and somewhat lesser Portuguese than I would be having to work with an interpreter. You can usually work through words and phrases that you don't understand better w/o a terp, if your language is at an adequate level and your non-verbal (cultural) communication skills and intuitions are strong. So, the investment, IMO, should be in getting as many soldiers as possible (given the MOS) capable of functioning in the host language rather than trying for the perfect terp.

Must be the FAO in me talking.

Cheers

JohnT