I definitely need a sleeping bag in April but I think you are really asking us to tell you whether you will need one. This may sound like I’m on my soapbox, sorry, but here’s what I think is the only way to reply to this question.
I think the "should I take a sleeping bag" question is the same as the "what are the best hiking boots" or "which backpack should I use" questions. This is a question that no one else can answer for you because it depends exclusively on your own body. I don't doubt that all of the posters have accurately reported on what feels good for them in those conditions, but they have their own unique internal heating and cooling systems. I always take a lightweight sleeping bag (850 grams), even last year arriving in Santiago in late July. But then I'm what the Spanish call "friolera", someone who gets cold easily. Only you know if that describes you too. If you're the one who always pulls out a sweater to warm up in summer air conditioning, or who needs extra layers when sitting around in the winter, then you will probably be very happy with the decision to carry a sleeping bag. If you sweat a lot and run around the house in shirt sleeves in winter, then you are likely to be fine with something much less.
There is also a gender difference.
While male and female body temperatures are similar, subtle biological difference conspire to make household temperatures a perennial bone of contention
www.theguardian.com
So my bottom line is that all I can tell you is whether I would need a sleeping bag. Which will be totally irrelevant for your decision whether YOU will need a sleeping bag. Buen camino, Laurie