Nothing is much better than these things, at shouting “tourist!” I know they seem to be a good idea, but they’re not. Especially if you have any desire to blend in at all with the local populace. The only people I’ve ever seen sporting zip-offs are tourists. And that can be ok if you want to remain immersed in a clot of your fellow zip-off pant wearers.
I’ve found when traveling, the more you blend in the better your experience of another culture can be. So, being somewhat sensitive to local fashion can help. For example in Mexico, as you travel inland from the coast, adult men don’t wear shorts. Sure, if you have blue eyes and freckles you won’t be mistaken for a local Mexican man even if you’re wearing long pants, but you don’t want to work against yourself either.
Zip-off pants are the tip of the attention drawing iceberg of bad travel practices. Last week I saw this article, How To Avoid Looking Like A Tourist, by Kate Kuhlman. The article covers almost every travel fashion faux pas from the wrong footwear to cameras used as necklaces. She beat me to it and did a good job on the subject, it’s funny too.
So remember, the people hawking travel wear like zip-off pants have their sales numbers in mind, not what you’ll actually look like outside of the shop or catalog.