If you are an American Citizen living or traveling in El Salvador and you should have your passport lost or stolen there is not much useful information on the Internet.
This should help:
You will need a copy of your passport and a photo ID from the USA (such as a state drivers license). If you do not have a photo ID then you will need a copy of your original birth certificate. The embassy will not help you get that so my recommendation is to use Vitalcheck (www.vitalcheck.com) to order it and then have a family member in the USA ship it here express (3-5 business days) with USPS / Fedex (about 50-70 dollars).
If you do not have a copy of your passport (big mistake), you will need to at least have the passport number and even then, it may be more complicated.
So now, you have a copy of your passport and one of the needed documents... how do you proceed?
If your passport was lost, skip this and go to the part that says "Dealing with the Embassy" below.
You must go to the nearest police booth for the PNC (El Salvador Police force). You have to report the passport stolen. You cannot request a replacement from the Embassy if you do not do this step. You will need to bring a Spanish speaking friend if you do not speak Spanish. You will explain what happened, they will give you a signed + stamped police report.
Dealing with the Embassy
You can print the replacement forms online. You need to print and fill out form DS-11 which is an application.
And also the Lost/Stolen passport form.
DO NOT SIGN ANY OF THE FORMS. YOU HAVE TO DO THIS IN FRONT OF THE EMBASSY INDIVIDUAL WHO ASKS YOU TO.
You can take your own 2x2 photo against a white background. Make sure head and shoulders show. Print it on photo paper and bring it. Or get a passport photo taken anywhere else for $5.00
Now, gather all the paperwork. If you do not have a way to print these forms you can go to the Embassy between 8:15 AM and 11:30 AM and ask for them. You will go to Window 4. They speak English. They will give you those forms and send you home to fill them out.
Making an Appointment
Now that you have all the forms, you have to make an appointment on their website (only way).
Choose Passport - Other services.
You can pick the day and time slot. You will show up to the US Embassy.
It is located in Santa Elena at the end of the Boulevard Santa Elena. Anybody in the country can tell you how to get to the gigantic USA Embassy.
You will enter the visitors entrance (not the entrance where all the people are waiting on Visa's).
Bring $135 dollars in cash or a CREDIT (NO DEBIT!) card to pay the fees. There are no ATM's inside the Embassy.
At the first security checkpoint expect to empty pockets and take your belt off - you can leave your shoes on. Present the appointment paper and also a form of ID.
You will be sent out the security checkpoint, walk straight back to a brown sign and turn left. Keep left until the second set of doors. You will walk in - repeat security procedure - and the guard will send you to the doors on the left. Walk through and head straight to Window 4 and present your appointment paper. You will get a number "A-xxxx". You will be attended by number. Remember, you have to be there between 8:15 AM and 11:30 AM those are the hours. Your appointment will give specific time.
You will get called to Window 1 or 2. Explain the situation briefly. The agent will take the papers - and give you the ticket for $135 to pay. Return to window 1 to pay it. You will be told to sit down - you'll be called.
When you are called, walk back to the Window that calls you. They will ask how it got lost or stolen - explain.
You will get a receipt with a proof of payment and a date written (It is 2 weeks - 14 days). You come back to pick up your passport on that date.
You get a full normal passport.
If you have travel plans sooner than 2 weeks they give you a temporary passport that servers only for a return trip to the USA.
General passport forms and resources: http://travel.state.gov/passport/forms/forms_847.html
USA Embassay in El Salvador: http://sansalvador.usembassy.gov/
Regular contact: http://sansalvador.usembassy.gov/service.html
Emergency contact: http://sansalvador.usembassy.gov/citizen-services/emergency.html