First you must search in the net which WU branches may be open and their schedule. Then,after your arrival you may call them and find out whether they have the funds. If not,you probably should make and appointment to collect the funds.
But be careful since teller employees are known to have ties to crooks. I would go directly first and if they do not have the funds,come back in a day or two.
I did not use WU, but collected similar amounts of money from MORE, but the downtown offices were all closed. I found three open branches in Liniers, about 8 miles from the downtown. MORE is connected with PAYPAL.