There aren't many people outside还是There aren't a lot of peop

两句都是对的.
many/much和 a lot of/lots of都表示很多.
在书面/正式场合,请使用many/much,而不是lots of/a lot of
在非上述场合.many/much 用于否定/疑问句.
a lot of/lots of 用于陈述句.