Found this tip today about how to ensure your iTerm console sends +Esc to weechat for the meta keys to work properly.
To make alt key bindings behave well for Mac OS X iTerm2, go to Preferences->Profiles->Keys and click +Esc radio button for option keys.
I like to use meta+c to clear a buffer and meta+x to close a buffer. meta for me is the Alt key. Here is the keybindings in my .weechat.conf.