Sistan and Baluchestan
(Please note that the information are mostly valid for Baluchestan. Though it is unlikely that the given facts differ much from Sistan.)
About Sistan and Baluchestan
Most people in Iran and other countries are afraid and if you check Iran's security description of your Ministry of Foreign Affairs, you might find out that they strongly advice against any travel - especially by land - due to risk of being kidnapped, killed by terrorists and/or the close distance to Afghanistan and/or Pakistan.
Once you put the fear aside, you will find a beautiful landscape and great people.
This province and its people is different from Iran. People are Sunnis and - apart from the big cities Zahedan, Zabol and Chabahar - still live in tribes. It is the poorest region in Iran. There are no gas pipelines, few jobs and people in Baluchestan rural areas basically live from smuggling Diesel to Pakistan. You will see hundreds of pick-ups with barrels on its back.
The government in Tehran just gives a fuck.
Near the three big cities (Zabol, Zahedan, Chabahar) you will find people who can speak English. On the countryside it will be very hard. You better speak Farsi.
Though Baluchis have their own language (Baluch), it is not that much different from Farsi, so you can somehow understand it. Baluch is a mixture of Farsi and Urdu.
The people are honest and although people will tell you, they don't do Taarof, you should not take it for granted.
Since this region is not used to tourists, people are curious and friendly which can resume in short waiting times. But refugees from Afghanistan are passing, too and people - since smuggling - are afraid of getting trouble with police.
Due to some attacks and kidnapping in the past and the proximity to Afghanistan and Pakistan, there are police check points (guns, spikes and bumpers) before each town, if not between towns as well. Most check points are run by Iranian, not Baluch people.
Accommodation and Sleep
People may invite you to their homes, though please don't take advantage of their hospitality. People are really poor here.
There's plenty of space in the nature next to the streets to put your tent. And in general there are more rivers than in other parts of Iran, too.
This is from Dec 2015 from redjo27:
I flew to Zahedan from Tehran and continued south to Chabahar, making a detour to Saravan and finally went to Bandar Abbas. I speak Farsi well so it was not a problem to talk to people are even the police.
Although there are many reports that people who are going to Pakistan are stopped at all the police checkpoints, need an escort etc I made totally different experiences: I'm always noticed as a foreigner in Iran (mid-long red hair). Still I never had no problems with the police. I was asked once (by Baluch police) to show my passport. I just showed them a copy and complained I didn't have problems the time before and they let me go. In Saravan I was taken to a police checkpoint (Iranian) and we had a nice chat (in Farsi) - no passport asked - before they stopped a car for me. But in general I had lots of respect of the police and often just out of sight of the checkpoints. In addition all drivers asked me before letting me in (sometimes wanted to see), if I had a valid ID.
However when I wanted to take a bus two times the driver refused for being a foreigner and another time, I was just not asked ignored at the station. So hitchhiking was the only option and it's a good 'excuse' why you don't take the bus. One time I took a taxi (near Sarbaz to Negur) which was 2,80$ for like 150km.
The road from Chabahar to Bandar Abbas is definitely doable by hitchhiking in one day (~11h). But truck drivers told me it's dangerous at night - possibly NOT (only) due to thieves but camels that run or sleep on the road.
Blog entry about autostop in Baluchestan