In a large pot over medium high heat, bring water and oatmeal to a simmer, add in a pinch of salt and mix. Once water is simmering, mix occasionally and allow oatmeal to cook until it begins to thicken, about 4-5 minutes.
Next, add in sugar and milk, lower heat to medium low and allow oatmeal to thicken a little bit more, about an extra minute before folding in remaining ingredients. Stir until cream cheese and guava have been incorporated.
Serve and garnish with cinnamon and guava, if desired.