I'd get a Beco. If you are worried about the heat, the Beco might be a better choice since it's made of cotton material rather than the canvas type material of the Ergo. Plus, I have also heard some bad things about the company lately which would cause me to NOT buy an Ergo.
I do think a soft structured carrier would be great for you if you want a really good comfy back carrier. There are a bunch out there, but the Ergo, Patapum and Beco are the 3 I'm most familiar with. My personal fav is the Beco (
www.becobabycarrier.com). LOVE ours. AWESOME carrier. You can cart a baby around on your back all day and not have discomfort. We carried my ds around in the Beco last year and it was perfect.
If you are going during the summer you could get solarveil mei tai. That would help with the heat. If you are going during a non-summer month, you should be fine. You will find a soft structured carrier to be so darn comfy!!!!! WAY more comfy with an older bayb for long carries than your ring sling. I loved our ring sling, but could not carry my baby for a long time after he got older.
A mei tai would work for you also, but if you want a back carrier, I'd get a ssc.