Which plan should I sign up for?  I need 1 form but will have over 100 people register this month.

3.  Which plan should I sign up for?  I need 1 form but will have over 100 people register this month.  It will only be this high during the month of May.  I wont have anyone register in June or July so I don't need any forms.   I will have people register in August/1st of Sept but not in Oct, Nov or Dec.  I will have people register in Feb, but not March or April. Is the Free package enough or do I need to move up to the Bronze?

You can upgrade to Bronze plan, which allows you 1000 submissions per month. You can cancel the subscription for the month you will not receive any submission to avoid the charges, and upgrade again for the month that you will receive submissions.

Just to let you know, if you have more than 500 submission, and you downgrade to free plan, you will need to download your submission data first: https://www.jotform.com/help/73-How-to-Download-Form-Submissions-as-Excel-CSV-PDF, because a free plan allows you to store only 500 submissions. So, only the 500 most recent submission will be kept.

Let us know if you need anything else.