3 months visa - and a trip to Mexico?

[Leyah]

If I went to the US for 3 months, would I then need a return ticket, or is it legal to go to the US with only the ticket overthere, and then later on pucharse my ticket to Denmark (home)?

Would it be legal for me, to go to the US for 3 months, go to Mexica for 3 days, and then return to the US and stay there for 3 months again?

I look forward to your answers

[immihelp]

1. It is better to come to US with return ticket.

2. Yes, you can do that.