Rule #1-don't lie. After that, you're good. Preference is time to pour it all out, presuming you're feeling it. That you love 2 houses is none of their business. If you can say wholeheartedly that you love them and would be thrilled to be a member, then say so. The fact that you might be saying the same thing to 2 chapters is completely beside the point. This isn't dating. You get to like more than one chapter at a time
And I'm going to jump ahead here a few weeks. You've gotten your 1st choice chapter, pledged and started establishing yourself in your daily life as a college student and sorority member. And the dew starts to come off the lily. Maybe you should have chosen the other house. These girls aren't nearly as fun or welcoming as they seemed during rush. There is no singing or crying every time you approach the door. THIS IS COMPLETELY NORMAL!!! Don't let this freak you out. Rush is not life and vice versa. A lot of girls get the post-rush blues, think it's the chapter's fault and drop out. HUGE mistake. Stick with it. This process is pretty fake and contrived but at the end of it and over time, what you end up with is good friends. But it's not instant.