Entering the U.S. under a B-1 visa is permitted after you have filed an I-526 petition. However, you must only be involved in those permissible activities such as visiting for a short period of time with the intent to return to your home country. and not coming to the U.S. with the intent to stay in the U.S, and adjust here to conditional permanent residency.
The B1 and B2 visas are non-immigrant visas, which require an intent to return to the home country. The I-526 petition is the first step to getting the Immigrant EB-5 visa. One must be careful in managing the two visas and entries into the U.S. Retaining an experienced EB5 attorney can help potential immigrants develop a strategy to meet his or her U.S. immigration goals.
Entering as a B-1 or B-2 is still appropriate for the EB-5 petitioner. It may actually be appropriate to say that you are looking after your EB-5 investment as a reason to enter as a B-1. IF on the other hand, you are coming to look for a new home (i.e. buy a house, condo, or co-op, etc... or temporary home (i.e. an apartment) or check ou the potential schools or daycare for your young children, then entering as a B-2 for pleasure OR B-1 on "personal business" is OK. It is best to keep proof handy that you intend to Consular Process, i.e. a copy of the I-526 showing that intent, correspondence from NVC or USCIS or the Consular Post is great to have handy. If at all feasible, visit your Consular Post and ask them if they could annotate your visa that you have legitimate business concerns related to your EB-5 investment in advance of immigrating on an anticipated EB-5 visa. They might refuse BUT they would be obligated to make an entry in a particular computer database which would then be accessible to CBP at a port-of-entry (POE). Such an entry would bolster your claim to CBP IF they gave you any hassle about it (which they probably won't).