Which hotel are you staying in? Why can't you travel across the city? You can easily walk into the city center, Zeil, Fressgasse, and Römer in under 30 min. or you can take a tram for 5 min. A group day pass for up to 5 people is only 9.90 €.
Recommended restaurants: Leib & Seele near the Hauptwache, Markt Stubb in the Klein Markt Halle (weekdays 10-1600, Sun. closed) Wein Stubbe on the Römer, Paulaner behind the Kaiserdom.
On the Kaiser Str. try Urban Kitchen, or the Fette Bulle. Saravanaa Bhavan is a vegetarian Indian place that I visit a lot.
On Münchener Str. there are any number of ethnic places, Indian, Turkish, Asian, Malaysian and Alim's Fish Market.
Head over to Sachsenhausen to Dauth-Schneider, Atschel, or FichteKranzi.
On Fridays, go to the Farmers Market on the Schiller Str. On Thur. & Sat. go to the one on the Konstablerwache