Add all the ingredients to a large measuring cup except for the cellulose gum. Mix well until the instant coffee grounds are fully dissolved and well incorporated.
Using an electric hand mixer on high, slowly sprinkle in the cellulose gum while the mixer is ON, so that the powder distributes evenly and doesn't clump. The cellulose gum works as a stabilizer and gives you a paleta that is creamy, not icy. This mixture is not meant to thicken too much after mixing, so don't worry if it looks a little too runny to you. Alternatively: Here's what I recommend if you're using cornstarch instead of cellulose gum. Combine the milk, crema, and sweetened condensed milk in a small sauce pan. When combined (no chunks), turn on the heat to low. Stir and do not let it boil, but once it's hot add about 1/4 cup to a small bowl with the cornstarch and mix until smooth. Then add it back to the saucepan and continue cooking over low heat, stirring until it thickens. Let it cool before adding the remaining ingredients.
Pour mixture into a sanitized popsicle mold. Slide in the popsicle sticks and freeze for at least 8 hours. To remove the paletas from the mold, place it in warm water for about 20 seconds to loosen. With a little wiggling and force, the popsicles will slide right out.
Store in the freezer for up to 2 weeks. You can keep them longer but they start to form more ice crystals and get harder over time.