Absolutely; modern Fortran is great and is syntactically rather close to Matlab (and to an extent R as well).

The main difficulty with Fortran is IMO the lack of an extensive standard library -- sure, you can find code out there to do almost anything, but then you need to figure out linking/calling conventions/possibly incompatible data models for each new library you bring in...

But, as another poster mentioned, it is quite straightforward to call Fortran from R :)