Yes absolutely, you can use your conditional offer of admission for visa submission. 99% offer letters are considered conditional especially when applicants are waiting for their final grades. If you wait to satisfy those condtions then obviously you will be missing those classes and visa officers know that. Just make sure that the conditional offer does not say that you have to complete an English Program (ESL) before the start of your course. I am assuming you have done IELTS or you're exempt. Conditions like, courses must be complete, or final transcript must be submitted are common. Don't hesitate and submit your application with the conditional letter. Print it out and attach it.
Hope this helps