El Salvador Passport

No, you should not try to obtain a VOA in Haikou. It is not advisable to rely on this kind of VOA because even the Chinese authorities are diminishing its importance in favor of 30 day visa free access. You are encouraged to make a contact with the relevant agency like Travel China Guide to see whether they would support you with 30 day visa free access. Also, you should be aware that you cannot travel to mainland China from Hainan without a proper visa. You can, however, obtain one while on Hainan, again with the support of relevant agency and after that proceed toward Beijing or some other mainland Chinese destination. From there, you are free to take a direct fly back to US. You can contact this travel agency by email or by Enquiry form.