Based on using a public clinic in Arzua: a) bring your insurance card if using the public system. They have no mechanism to accept cash. They don’t really care if they ever get paid, but need to submit something before they see you. B) if using the public system, plan to be in a large town with a hospital, rather than Centro de Salud for a more likely quick turnaround. C) plan to be in a town with a good private Dr and private lab when you need them done, D) perhaps plan in a rest day so that you can get your results, e) ensure that you know how to ask for what you need in Spanish if not using an expat focused service (I needed a lot of my Spanish at the clinic), including how to get results, etc. they can probably email them- I emailed the photo of my insurance card while at the Centro de Salud.