On the U.S. side, both I-5 and I-805 connect San Ysidro to the communities to the north. You can drive to the border crossing and then continue driving through, or park at one of the lots and walk through. Parking at one of the lots costs about $4-$9 a day. Traffic is pretty heavy coming up from Mexico.
The San Diego Trolley (http://www.sdmts.com/Trol...) Blue Line service connects San Ysidro to Chula Vista, National City, and Downtown San Diego to the north. Standard one-way fares run from $1.25 to $3 depending on how far you travel. Day passes run at $5, and there are 2, 3 and 4 day passes available.