I can get off the subway or bus one stop away from my destination, so we could save some gas.

语法上没有大毛病。但是句子前后关系有点问题。

建议改为：if i get off the subway/bus one stop away from my destination, we could save some gas.
或者
I'll get off the subway/bus one stop away from my destination, so we could save some gas.
或者
By getting off the subway/bus one stop away from my destination, we could save some gas.

另外主语前后要一致。
到底用i还是用we要决定好。

一切要看你具体要表达什么意思。