Some do preach the truth about salvation, and there are many that do not. Some add a gospel of works into the mixed - must be baptized in Jesus' name, must speak in tongues - and some are just plain off in their theology (some in major ways, teaching we are all little gods, Jesus suffered in Hell and was born again there, name it and claim it theology - and of course, believing sign gifts are for today, which includes believing that the Bible is not complete and people are getting new revelation today in the form of prophecies, dreams, visions, etc.).
To sum it up: some particular people in charismatic and pentecostal churches may be saved, and there may even be specific churches that are closer to the truth than others - however, they are such a horrible mess of false teachings and dangerous signs and wonders, it is better to steer clear of them.