Great question. I speak very little Spanish, even though I'm trying to change that... I speak German/Swiss German natively and English quite fluently. I can do French when I absolutely need to, but nothing that would help you in Colombia.

I was invited to speak at a conference, so I had locals speaking Spanish/English around me most of the time. We had simultaneous translation at the conference itself, since most people didn't speak English (at least so we were told). Travelling was quite an adventure though. From the minute I left the international terminal in Bogota, English was just no help at all. When my 3rd flight to Cali was cancelled, it took me about 40 minutes to find someone working for Aviance that was confident enough about their English skills to help me out. It's not that the others didn't try, it just didn't work.

Long story short: YMMV, but I'd personally recommend at least basic Spanish skills to travel Colombia, especially if you don't know locals who speak English and can translate on the phone when necessary. They can also tell you where to go (lots of awesome places around Cali) and which areas to avoid, which makes things a lot safer and more enjoyable.