Ask any missionary who works in remote areas or with Moslems, they will tell you that God does indeed still use dreams to point men in the direction of the Bible and salvation.
It will always be, like you said, according to Scripture.
This is true in many cases. We support missionaries that live in Islamic countries, and they will attest to this happening.
What Peter said 2:16-21 about dreams was only partially fulfilled on Pentecost.
Here's what the Life Application Bible [(c) 1996 by Tyndale] states: "
2:16-21 Not everything mentioned in Joel 2:28, 29 was happening that particular morning. The 'last days' include all the days between Christ's first and second comings and is another way of saying 'from now on.' 'That great and glorious day of the LORD' (2:20) denotes the whole Christian age. Even Moses yearned for the Lord to put his Spirit upon everyone (Numbers 11:29). At Pentecost the Holy Spirit was released throughout the entire world---to men, women, slaves, Jews, Gentiles. Now
everyone can receive the Spirit. This was a revolutionary thought for first-century Jews." (Note on p. 2121.)
Today, of course, one needs to examine what dreams mean in the light of the
completed Word of God (which they didn't have at Pentecost).
If a dream does lead a person to having a desire to receive Christ as his Savior and subsequently live for His glory, then I'd say it's a valid dream. OTOH, if it doesn't, then I'd seriously question that it came from God.