Do Southern Chinese speakers have any greater propensity towards using 啦 than Northern Chinese speakers? I'll provide some context that leads me to suspect this. I am the American born son of Overseas Chinese who were born and raised in Myanmar. The dominant household language ended up being a mixture of the Taishanese variant of Cantonese and Burmese, but I still have limited exposure and understanding of standard Cantonese. I took Mandarin in college and spent a year living in China and I'm not sure what kind of accent I accquired when speaking Mandarin, but it isn't quite American and it isn't quite the stereotypical image of an Hong Konger speaking Mandarin.

Anyways, I heard 啦 in Taishanese A LOT growing up and I don't know if this is element is also common in standard Cantonese, but I have heard Malaysians speaking English and inserting 啦 to the end of things. One of my habits when speaking Mandarin is to insert "southernisms." I think I subconciously gain a sense (maybe a false one) of comfort and fluency when I say "哪里" instead of "哪儿" and I even will say ridiculous things like “马马虎虎" because it vaguely reminds me of the sing-song in Cantonese. There's been moments too where I had to refrain from saying stuff like 冇 or 喺唔喺? to people who CLEARLY spoke Mandarin. 

So do southerners actually say 啦 with any greater frequency? I've never heard Singaporean Mandarin, but does that include a lot of 啦? Is this a real thing where southerners take something that sounds equivalent in their native dialects and sprinkle it into their 普通话 or am I an odd one? My real, personal question then sounds something like -- is it viable for me to add 啦 to the end of many sentences? I understand 啦 to be a bit of a suggestion, sort of like 吧 except I never heard people on the Mainland say 啦 with the frequency they say 吧. BUT if I were to do this, would I sound extremely strange to say things like “我们去吃饭啦” or “你说啦”？
So do southerners actually say 啦 with any greater frequency?


Yes. Cantonese people and their excessive usage of 啦 is already a widely known stereotype.


  I've never heard Singaporean Mandarin, but does that include a lot of 啦? 


The standard dialect used in news broadcasters are quite similar to Mandarin in China. 啦' s usage in daily speech may vary, depending on your background.


  Is this a real thing where southerners take something that sounds equivalent in their native dialects and sprinkle it into their 普通话 or am I an odd one?


It's a real thing. Not just southerners, everyone in the world has a natural tendency to do so.


  Is it viable for me to add 啦 to the end of many sentences?


Excessive usage of 啦 in Mandarin is like excessive usage of "You know" in, you know, English, It's, you know, kinda annoying. While I applaud the usage of dialectical phrases in Mandarin, using 啦 excessively is only an indication that your Mandarin needs improvement.


  Would I sound extremely strange to say things like “我们去吃饭啦” or “你说啦”？


Not really strange because most people know too well how a southerner would speak. Still, it's better to use "我们去吃饭了", "我们去吃饭吧", and "你说呢".