for the moment , its better than nothing! thats for sure

but id change my routine a lil if i were u, id go something like this
4 sets of 10 - 12
mon - chest (flat press, incline press, flies, decline press) this day, with out much weight and a bench will be kinda .....just doin to do it heheh
wed- biceps/back ( bent over rows, chin ups/pull ups, dead lift, standing curls, preacher curls, hammer curls) (should be able to get most of this goin)
fri- Tricep/Shoulders- dips, tricep extensions , or kickbacks, skullcrushers, overhead shoulder press, side flies, front flies, upright rows,) should be able to do all those exercises with the dumbells, and a chair hehe
sat - legs - ham string curls, quad raises, calf raises, squats, lunges, ( should be able to do most of those as well)
but , to do alot of the proper lifts you will need a bench and more weights

cuz with out one its gonna be tuff to do things like.....ham string curls, quad raises, shoulder press, incline bench press, decline bench press, chest flies, etc.
im sure some of those excersises u can rig something up .