Hooking up help

I'm going to be hooking up with a guy from CL soon. I'm negative and he says he is too, but... can't know for sure. If I plan on just blowing him, should i still make sure he wears a condom?

I've read that you can still contract certain diseases from giving head, even before ejaculation. Should I take his word for it and go without condoms or be safe regardless?

Pic not related, but I figured everyone here might like it. I'll post some more like it as well/