Excluding MegaSilver, the enemy until near the finale was unaware of the Megarangers' secret identities.
The enemy was always aware of the Space Rangers' secret identities.
Usually addressed each other by ranger designation (i.e. MegaRed) while in costume.
Addressed by actual identity (Morphing Complete) while in costume.
Receive their Mega Suits from the transmissions from INET's satellites that sends their Mega Suits over to them when their transformation device (Digitizer, Keitaizer) is used.
The Space Rangers, excluding the Silver Ranger, require the transmissions from the Astro Megaship to use and maintain their powers.
After their secret identities were exposed almost everyone turns against them out of fear for their safety, turning the team into pariahs, though in the end the people of their high school are able to see the error of their ways and cheer them on.
After they expose their secret identities to the people during the final battle, the people are able to support them and help them bring down Astromena's army with no kind of difficultly whatsoever.