Your essay has some minor, yet significant, grammatical issues. Also, your last sentence is completely washed out by your in-depth discussion of your tour guide duties. I would focus less on the tour guide and more on your clinical experiences. You can write a couple of sentences about your tour guide position, but the other 200 or so words can be put to better use describing how this experience relates to your clinical experiences and why you want to practice medicine.
Remember, 250 words is a suggested limit. You don't actually have to write 250 words unless those words are going to add value to your essay. Don't glorify a position, but do describe your job succinctly (i.e. I don't think it's necessary to mention the Angels).