Regular cannabis use has a twofold effect on sleep: THC, the active compound in cannabis, has been shown to decrease the amount of REM sleep that users undergo and 2) that lost REM sleep is filled in by longer periods of stage 4 sleep. In other words, regular cannabis users will have fewer dreams but will have deeper, more restful sleeps. (reference) Early research found that cannabis temporarily increased deep sleep, suppressed REM sleep, and resulted in a REM rebound upon discontinuation. More recent studies confirm that cannabis can reduce sleep onset latency and that it suppresses REM sleep, resulting in a REM rebound upon discontinuation. Heavy cannabis users were found to have generally disturbed sleep as well as a reduced REM latency indicative of prior REM suppression. (reference)
So, in summary, you should expect it to be particularly difficult to experience lucid dreaming if you are a continous weed smoker. But the good news is that you may get serious and vivid lucid dreams if you quit, even temporarily for a few days!
See also: Bibliography, Booze and dreams, Dream cycles, Dream glossary, Dream recall, Dreams and brain disorders, Dreams as a source of inspiration, Food and dreams, Herbs for dreaming, Hypnagogic state, Lucid dreaming, Neuroprotective agents, Precognitive dreams, Recurring dreams, Shamanic dreaming, Sleeping brain, Sleep deprivation, Weed and dreams, WILD, Yoga Nidra