No, you can not.

If you don't have a separated search bar, your only options are enabling or disabling autocomplete. There is no option of using autocomplete just when you want it.

Also, the local autocomplete of the address bar is great. Count me as another one that does not want to miss it.

I was letting him slide with exactly that: an on/off switch. But with additional configuration one could use a 'g ' prefix to activate autocomplete via Google, for instance.