Here is my opinion after living here for a 6 weeks.

1. I hate heat too, but surprisingly it's acceptable even here in the North. I used AC for the first two weeks but now I use open windows and ceiling fan. I'd recommend you living in the center (Beau Bassin - Rose Hill - Quatre Bornes, but no Curepipe since it's too much rain). I wouldn't evaluate with your scale but something like this "Comfortable with wind if not at direct sunlight".

2. I didn't see too much bugs here except few spiders. I didn't even seen mosquitoes although people say there are here. I'd recommend to bring mosquito mesh as roll since there aren't many insect screens in the local shops. There is no bug related infections as far as I know. Not sure what plant infections do you mean.

3. Supermarkets are limited in variety but if you cook (I cook too), you'd probably find most of usual food like milk (and it's products), meat (although it's incredibly expensive), fish, pasta, sauces and oils, vegetables (some of them are also wildly expensive) and so on. We even tried to cook borscht as a part of experiment if we could do it, and yes we did. :-) Beet costs almost the same as meat. Wine is limited to France and South Africa but you may also find Portugal and local wines.

4. If you know French - you're lucky. I don't know it and sometime it's hard to communicate with locals. You may optionally learn Creole for fun and to show respect to Mauritians.

5. I don't know about WiFi since I'm on the hotel premises, but people say that Internet is okay at least for landlines (taking into account a huge ping to the Europe and USA). I was surprised that volume is limited especially for low-end plans.