I don't have time to give specifics right now, but I've been to Sarajevo twice, each time for several days and eaten at lots of restaurants.

Click on my name and scroll down to look for my trip reports where you will find lots of restaurant information and details.

I've also been to Mostar several times now, but never for more than an overnight, but again, you'll find details in my trip reports.

Also check out vttraveler's threads and posts - she has also spent time in BiH and has some good suggestions.
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http://www.fodors.com/community/europe/mostar---a-city-of-beauty-and-bullet-holes.cfm

http://www.fodors.com/community/europe/off-the-beaten-track-in-bosnia-and-herzegovina-juliat-explores.cfm

http://www.fodors.com/community/europe/sarajevo-in-the-springtime-juliat-makes-a-return-trip.cfm

bookmarking

My trip report from 2010 has some restaurant suggestions in Sarajevo and sightseeing ideas around that city and Dubrovnik

http://www.fodors.com/community/europe/trip-report-bosnia-and-herzegovina-croatia-in-october-2010.cfm

I don't remember many vegetarian options unfortunately.

I wrote some about the route I think you are taking back to Dubrovnik via Trebinje. It is scenic but you should be cautious about stopping along the route due to danger from unexploded land mines

Visitors in Dubrovnik who want to do an excursion to Mostar have option to visit Mostar via Trebinje in Bosnia and Herzegovina with connection in another bus which depart at 14:30 from Trebinje Bus Station.

Libertas bus from Dubrovnik for Trebinje departs at 13:15 and it is at 14:15 in Trebinje. Next to the Bus Station in Trebinje there is TIC (Tourist Info. Center) where you can quick pick-up broshures. Trebinje is rich with cultural-historical heritage, also.

There is open market where local people from Dubrovnik use to went to buy natural vegetables and fruits for their kitchens.
That was before the Balkans wars. I don't know whats happening now.

At open market I recommend absolutely natural honey of herbals, vines from monasterie's production, all other info at TIC.

Returning from Mostar to Dubrovnik. When reach Mostar Bus Station - East, go to see TIMETABLE for return. From the first June started High Tourist Season and there are many buses which are passing trough Mostar toward Dubrovnik and Montenegro coast with STOP in Mostar.

Regards,
@kostake