If you are driving, make sure to get your Mexican Auto Insurance before you cross the border.
The tollgates take US money but nothing larger than a $20 bill.
You do not need a tourist visa but you will need an approved government-issued ID to get back into the USA. Your passport is best.
Go South on I-5 or I-805 and stay on it until you reach the border.
Cross the border at the San Ysidro Border Crossing in any lane. If you get a red light you will need to pull into secondary (the inspection area), but most likely you will get a green light and you just keep going.
The next quarter of a mile is the most confusing of the whole trip. You need to get this right it’s really not that difficult, just sounds like it!
As soon as you are across the border and are in the lanes to leave the inspection station, move to the far right lanes for the exit marked "Rosarito/Ensenada".
As you take the exit ramp right then up and over, you will be merging onto the road that runs west, along the border.
Follow the border road for maybe a mile and a half. You will go up a very steep hill, with lots of slow traffic! As you come down the other side of the hill, there will be an exit off to the right at the bottom that directs you to Ensenada. Take the first exit and be careful merging into the traffic at the end of the ramp. There isn’t much room. After merging, as soon as you safely can, get in the left lane.
You will travel maybe another mile or mile and ¼, the road will split and the two right lanes exit into another community called Playas Tijuana. Stay in the left lane and follow the curve to the left. If you are in the left lane you will have no trouble with this. After the curve you will come to the tollgate. The toll is about $2.20 US Dollars (varies with the exchange rate) or $31 pesos (they do not take mixed currency for the toll – just one or the other). Maybe at this point you have driven about 5 miles. FYI, there are clean and safe restrooms on this highway, look for the blue signs.
Stay on the toll road following the signs to Rosarito/Ensenada. It really is a pretty drive along the coast. There are several American enclaves all along before you get to Rosarito. Just stay on the toll road!
Take the 4th Rosarito Exit, labeled "Rosarito Sur" (South Rosarito) under the big white archway welcoming you. Use caution as the exit ramp has a sharp right turn.
Continue west toward the ocean until you reach the main 4-lane street with a landscaped median, Benito Juarez, about 2 blocks. There will be a stop sign there and directly across the street will be the Rosarito Beach Hotel and Resort with another big white archway.