Salvia is not scheduled, controlled, or regulated by the DEA or FDA in the US. Only the states Louisiana, Missouri, New Jersey, and New York have enacted state controlls on it. Internationally, there are varying levels of control in:

Australia
Belgium
Denmark
Finland
Italy
South Korea
Sweden

For once the archaic US government fell behind the rest of the world on controlling something. Its about time. If they would only unschedule some things...

Also, I imported some from Mexico very recently and had no trouble at all, it wasn't even in stealth packaging. Trying to hide it might actually draw more negative attention if discovered than if it were just in a regular package. Just make sure it isn't marked for consumption (in which case the FDA has jurisdiction over it). Any Salvia confiscated by customs under the Controlled Substances Act is an illegal confiscation.