What's the best way to buy Blackcoins with cash?
buy bitcoin at an ATM and exchange for Blackcoin.
There's no bitcoin ATM near me.
Localbitcoins.com has been a place to advertise buy/sell BLK in the past. Put it in with an offer to buy/sell BTC.
You can buy/sell BLK for cash in person. You can find a seller anywhere online then send cash or money order via mail and use BlackHalo to secure the transaction. That's one of the great things about BlackHalo/BitHalo is that there is no longer any need for centralized exchanges. With Halo you can securely trade peer-to-peer.