I use my Fairphone in German, but regularly type SMS, emails, tweets, posts also in English. Spell check and autocorrect are a nuisance when typing in English, although not always and I have not been able to figure out whether the OS or the applications can detect the language I type. Any easy way to swap languages on the phone?
in advanced settings (system settings > language input > icon besides the AOSP Keyboard (or wichever keyboard you use. most will have this option) > Advanced Settings you can tick “Language switch Key”.
Now if you have multiple input languages in your Keyboard Settings there will be a language switch key besides your space button.
You could also use a keyboard which supports two languages at once. I don’t know about SwiftKey, but I tried Swype, and it does. And does the job pretty well, most of the time. (Caveat: be sure to restrict the apps rights, using the settings and to be sure also XPrivacy, as the bloody thing wants to transmit your data including location to their servers.)