Your instincts are excellent here. There's a rich variety of strong vocational English books, and a few specifically targeted for hospitality industry. Levels, of course, matter.
"Day by Day" probably remains the most popular general VESL textbook. It provides 6-10 variations of practical, everyday work situations in a communicative style. Adding a picture dictionary and workbook for lower level (maids, etc) speakers is also recommended. The Oxford University series remains my favorite.
For intermediate and more advanced English language learners, you can explore some more specialized textbooks like the U.S. Department of Education books created just for hotel workers. (I can't recall their title, but check Amazon or the Department of Education website.) You might also check
OTAN - set up by the California Department of Adult Education for materials. If the students are interested in more management type positions, you might also take a look at the outstanding English for Business book in the Professional English series from Thomson.
You might also checkout the language software program called "English on the Job" that has developed a solid reputation among vocational schools in California. Finally, you might check to see if the local unions provide free workshops and/or ESL classes. I helped design some vocational workshops this summer for low level English language learners in Los Angeles hospital workers. Sometimes these tailored courses can cover far more ground - in a friendly, less stressful manner - than other ESL courses.
As the economy tightens, I expect the need for adult education and VESL programs to dramatically increase. Let's see whether if Obama administration chooses to invest in these new workers, expands English language programs, and promotes comprehensive immigration reform. Keep your fingers crossed.
Good luck!