Wow... I am floored by your comments on Bolivian food. You clearly did not try the right places. You should try the Dumbo Ice Creams. very good on all flavors I have tried except for the Vanilla.
Also for food, The saltenas are fantastic in Los Canguros. Almost any dish served up by the restaurant Miraflores or the Suiza is going to be good. Miraflores is more traditional while the Suiza serves up more elaborate dishes such as trout and Surubi. My son ate the Surubi on his first trip there and said it was the best meal he has EVER had.
The Duck at the miraflores is alos very very good. We ate there maybe 10 times over 3 trips and were never disapointed.
Naturally when you start to get into deep jungles and river towns like Rurrenabaque, your expectations must go down. There simply is not the demand in places like that for great meals.
In Bolivia you should try the beef. It is very good and different taste. The Lomo is the best cut. Also try the Picantes. They make it with Chicken, Duck, Tounge, and/or rabbit. In Cochabamba, try the Fricase. It can be pork or chicken (usually pork).
Some great restaurants there are The Suiza (on the prado), Miraflores restaurant, and Casa Del Campo (in the Recoleta) more touristy but still ok with English menues).