VPN Solution for my current Situation.

[perikillo]

  Hi people.

  I want to know which is the best VPN solution i need to my current
situation:

2 Offices  1 Mexico-Tijuana 1 E.U.-Otay Mesa(both in the border).

In E.U. Offices with have:

DNS+Firewall+Proxy  Linux
Mail Server Linux
Samba Linux
PBX Altigen Win NT
ERP DBA Linux
Backup FreeBSD.

Mexico
PBX Same system
Samba
ERP DBA(This is the busies from both sites)
Backup FreeBSD

65 User 55 Mexico 10 E.U.
   40 user in Mexico have mail account && only 15 Internet access
   all the users in E.U have mail account && Internet access.

We share files, E.U. users access the ERP system in Mexico.

If the users in Mexico need Internet, they have to reach the proxy in E.U.

Both PBX systems have communication for company internal calls, external
calls.

All this communication of Voice and Data goes over one private link, but
next year our contract is going to finish, them we need to negotiate the
next contract.

Another thing, is that we are planning to start the VoIP solution and see is
we can remove our current PBX system with Asterisk.

My  questions es this: Supposed that we continue with the same Private Line,
and we add another public line to do some VPN between both facilities if one
link fail the other can continue(backup) or have both sharing the workload,
with this workload which VPN solution is the best for my situation:

IPsec, OpenVPN, etc?

Speaking of FreeBSD, because there is where i want to deploy the VPN
solution in Mexico, in E.U. we have there Linux, this can be problematic?

Hope you understand my layout && english, any advice is welcome, thanks all
for your time!!!