You can have tropical fruits, yes, but just be aware of a few things.
1. Watermelon is high Calorie High GI, so moderate it.
2. Fruits don't combine too well with other foods, so give Fruit 10-15 minues to digest, and with Cirus Fruits especially, as you may have a slightly compromised situation there, because Citrus and Cereal may possibly lead to Hyperacidity, which if so, could increase the possibility of GERD, (Acid Relux), and associated Heartburn. Something I read once about the two Enzymes for both competing.
3. You could try to get things like Pink Grapefruit, or Pink Guava for example. They are good, especially for the Carotenoid Lycopene, which has been touted as possibly anti-cancer, and also helps destroy skin aging free radicals, so it might help to prevent the possibility of things like Oxydative Stress, (potentially more damaging Free Radical activity from reduced Anti-oxident levels, or increased F R levels).
Also Pink Guava is the best source of Vit C at around 165mg's.
Mango is also a good one for Carb content, it's quite high, I think about 25g's approx from memory.
Some Fruits have lower, like Oranges, Tangerines or Satsumas, that are about 9-12g Carbs approx, and may require an increased Carb content from other non- Fruit sources to boost your morning Carbs up, particularly first thing when Blood Sugar is low.