Good morning, I would like to assist you today.
I think that the first step is to make your daughter aware of your grandson's use of language, if she doesn't know already. A child his age is barely learning language, and in now way should have these kinds of words in his vocabulary, especially not toward using at an adult (even more his grandmother). This tells me that he obviously hears this kid of language regularly. Your daughter needs to be aware of this so that she can watch her own language around him, and be aware of the other influences that he may hear this from, including music and television.
Secondly, I recommend that you speak to your grandson about his cursing at you. The next time you see him, tell him, "The other day, you said some very mean words to Grandma. Why did you say that?" Allow him a chance to answer, and explain to him that those words are bad words, and they hurt people. Explain to your grandson that you love him, you never call him those names, and that you never want him to call you those names, or say those words again. Let him know that if he does, Grandma will not want to get him anything, or even be around him.
Also tell your daughter this, as I am sure she wants (and needs) her son to spend time with you; this should make her willing to work with you, and hear your suggestions about how to change his behavior. If he does use this kind of language again, directly addressing the language at that moment is the best option. I know it might not always be possible, but if you are in a similar situation (at a parking lot, then he curse at you); stop and correct him right sat that moment, and then if all possible, turn around and and take him home; same as like you want to do at a park or somewhere. I do think that is a good idea.
And please excuse the typos in what I have stated above; if anything is unclear or confusing, please let me know so that I can provide you with clarification.