My (Brazilian Portuguese) dictionary Aurélio does have an entry for garage:
- V. garagem
so garage seems to be an accepted spelling for garagem, but let's look at actual usage.
The CRPC (Corpus de Referência do Português Contemporâneo) lists
garage 128 results garagem 1008 results
and many of these are actually
- part of names (e.g. Paradise Garage)
- decidedly English (e.g. Underground garage)
- or refer to the musical genre "garage [house/rock]" (e.g. ritmos garage)
so the actual results are more like
garage <10 results garagem 1008 results
some of which may just be misspellings. Quantitatively speaking garage would probably be considered incorrect (when referring to garagem, and correct when referring to the musical genre "garage [house/rock]").