Almost all distributives give you tools to make possible to switch a language. Sometimes it’s a plugin in the tray panel. Or it can be some settings in special application.
But if you use specific desktop environment, you probably don’t have it. For example, in OpenBox you have only windows decorators and start menu.
Example of US / ES switching using ALT+SHIFT
setxkbmap -layout 'us,es' -option 'grp:alt_shift_toggle,grp_led:scroll'
Also may be useful: