For the more paranoid, LibertyX is a great alternative to Coinbase or other online exchanges. Purchase a QPay pin from one of thousands of their partner stores (usually cell-phone shops that sell prepaid SIM cards) with cash, put the pin into their app, and enter the address you'd like the bitcoin sent to. It's instant as well - Coinbase can take up to a week if you pay using a connected bank account - which can protect you from bitcoin price volatility.
Trading that into Ethereum is relatively simple - use kraken or any other bitcoin exchange.
