Problems decrypting my bitcoin-wallet on android
If you didn't see the error message bad decrypt, and if the garbage you saw had the string org.bitcoin.production, then the decryption worked.  In recent versions of Bitcoin Wallet, as explained in the README, the wallet backup is no longer encrypted plain text but a custom protobuf format.

You can write the decrypted wallet to a file using the -out option to openssl, which is probably more useful than dumping it on the screen.  However, if you want to read it or extract the keys manually, you'll probably need special tools, which I am not sure if anyone has written.  See also Is there a known way to export my wallet private key from the &quot;Bitcoin Android&quot; app (com.bitcoinandroid)?, though it may or may not be current.

If you did see the message bad decrypt then you got the password wrong.  Try other variants.

The intended way to use the encrypted backup file is simply to copy it back onto your phone and restore it into the Bitcoin Wallet app with the "Safety:Restore Wallet" option.  You don't need to manually decrypt it with openssl unless you are trying to do something fancy.