The Dean would probably prefer that they are not there more than even you do. It is, as mentioned, Freedom of Speech. It's a public setting. The College can restrict/assign them to a specific location.
If you really want to "stir the shit" engage them in conversation about objectionable issues but have your "ammunition" at your side.
What is the JW opinion of the UN? Do they support their stand for World Peace? Then why were they an NGO member? (Have letter from UN readily available.) Doesn't that make your religion a "hypcrite"? Quote Jesus' words about hypocrites.
It is true JWs shield child abusers? Is it true they are using MILLION$ of the dollars collected for the WWW to settle child abuse claims? (Have news articles ready on Conti and Lopez cases &/or records from ARC testimony.)
Aren't you always Bible Thumping about the End of the World being imminent? But haven't you been saying that for over 100 years? (Have WT publication quotes readily availalble about 1914, 1925, 1975, "end of 20th Century") Doesn't that make you False Prophets? (When they say no) THen you must admit you are LIARS, even if NOT false prophets. Doesn't you religion claim to be equal to the Prophet Ezekiel predicting the final days of Jerusalem? (04/01/1972 WT pg 197) So, then doesn't Deut 18:20-22 apply (False Prophets).
Try to have any friends you have on campus join you and listen/observe. Explain to them your motive. Make it uncomfortable for the JWs. You might be able to "plant some seeds".
The greatest revenge is living a happy & successful life!