I haven't been to either since 2011 so I am sure a lot has changed but Paraguay seemed like a great place with a lot of nice, sweet, feminine girls. Being in Asuncion is like being in a 3rd tier city elsewhere.
Uruguay I was only in Montevideo for a few days and I didn't get a great vibe from the women. They were cute and all but something was off for me. Just my experience.
Outside of those 2 countries I think Northern Mexico is great. I used to work in a smaller northern city that many would consider dangerous but it wasn't so bad in 2013/2014. I was out and about and never had any issues. I will say that these cities even if they have 1 Million only 100K are, how do I say this, "at your level".
You have to get involved in the community in these smaller tier cities, you can't just be bouncing around and find a serious wife. This goes for most countries btw. Become part of the community somehow. Maybe volunteering.