Yes, ALL does mean all who are of faith! It certainly does not mean that evil unbelievers shall also receive the Spirit sent from Christ. You bear false witness through your understanding of the word "all"!
We do see there that when the Holy Spirit was poured out, observers began to question what all that was about
Peter said that what they were experiencing was that which was spoken by Joel here
Acts 2:16 But this is that which was spoken by the prophet Joel;
Acts 2:17 And it shall come to pass in the last days, saith God, I will pour out of my Spirit upon all flesh: and your sons and your daughters shall prophesy,and your young men shall see visions, and your old men shall dream dreams:
Acts 2:18 And on my servants and on my handmaidens I will pour out in those days of my Spirit; and they shall prophesy:
Followed by his testimony of Jesus Christ and when asked what they should do it says
Acts 2:38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins,
and ye shall receive the gift of the Holy Ghost.
And again,
Acts 2:39 For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.
And after they heard, and believed even as Paul said,
Ephes 1:13 In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation:
in whom also after that ye believed, ye were sealed with that holy Spirit of promise,
And so after they believed they were sealed with the holy Spirit of God
Ephes 4:30 And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.
The Holy Spirit is the living water those who believed in Him would recieve after Jesus was glorified
All flesh to me is those who believe whether in nation of Israel (to whom he was sent) and beyond (all nations)
or the Gentiles (and so all flesh).