I hope the locals will chime in, but....
English is the language spoken by most visitors coming to dive on the Bay Islands. You may see a whole lot more folks speaking German who come to vacation. A few resorts on Roatan cater to Italian and South Americans, but I think an American trying to speak Spanish might be well in second place for any job considerations. Conversational Spanish might be a totally different lexicon than trying to coax someone into attempting to stick their heads underwater.
The Bay Islands are indeed a "Department" of Honduras, which is a Spanish speaking country, but traditionally the language of the Islas de la Bahia is indeed English... providing for a peculiar dichotomy. With the influx of the mainland worker class, that is changing rapidly, certainly in the service class and for sure in pop culture.
Tough enough to find any job if you are a well-trained and competent IDC graduate. I would recommend to stick with the SCUBA Books.